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163 ACT Vocab Words You Must Know


Many students are aware that you need a good vocabulary to do well on the ACT, but they're often not sure just how their vocabulary will be tested. Gone are the days where you needed to learn the definitions of dozens of obscure words, but a good vocabulary is still key to excelling on the ACT. To help you out, we've compiled a list of 163 key ACT vocabulary words to know. We also explain how vocab is tested on the ACT, the types of questions you'll see, and the best way to study ACT vocab words.


How Does the ACT Test Vocabulary?

Standardized tests in general have shifted away from emphasizing vocabulary, and the ACT is part of that trend. Whereas before it was common to have questions that directly asked you about the definition of a word, there is now much more of a focus on understanding words in context, rather than being able to rattle off dozens of word definitions strictly from memory.

However, a strong vocabulary will absolutely help you on the ACT, especially if you're aiming for a high or perfect score. Even if fewer questions ask directly about word definitions, an expansive vocabulary will help you read through passages more quickly and have a more solid understanding of the topics they're discussing.

ACT vocabulary questions are now primarily focused on testing your ability to understand and define words in context. You may see them in either the Reading or English sections.

Some of the words you'll be asked about may be unusual, but most or all of them should be known to you. You'll no longer be expected to know the definitions of obscure words that you rarely hear in normal life. Question 19, below, is an example of an ACT English question you might see. This example comes from an official ACT practice test.


To answer question 19 correctly, you'd need to know the definitions of cumbersome, thorny, strenuous, and gawky. You've likely heard or read each of these words, although you may not be rock solid on every definition. You also need to get context from the passage to answer the question. If you read through the entire passage, you'll learn that the Navajo code was much easier to use than previous codes, so you know the best answer for question 19 will be a word that contrasts with "simple" or "easy." Cumbersome, defined as "unwieldy" or "burdensome" is the best choice, so the correct answer is A.

Here's the type of vocab question you might see in ACT Reading:


Humor is a word you know, but all four answer choices could be correct depending on the context. You'd need to read the passage and understand which option fits the context best to answer the question.

As you can see, the vocab words tested on the ACT don't often go beyond a medium-level difficulty, but you still need to have a solid vocabulary and understand how to define words in specific contexts.




163 ACT Vocabulary Words to Know Before Test Day

Below is a table of the 163 top ACT vocabulary words to study and know. For each word, we include the definition and an example sentence that contains the word so you have more context for it.

To compile this list, we read through every publicly available official ACT practice exam and looked at both the Reading and Writing sections (and not just the questions but the answer choices and passages, too). We also used our own knowledge of the types of words you can expect to see most often on standardized tests. 

Though you don’t need to memorize every word in this chart, familiarizing yourself with most of them will help you better identify the tones of passages and make you more efficient at interpreting and answering questions correctly on the ACT.

Example Sentence
Present in large quantities
Living next to a lake means we have an abundant supply of water.
Correct; free from errors
Make sure your address is accurate before submitting your online order.
To come into possession of
When my grandfather died, I acquired his baseball card collection.
Refusing to change an opinion
The defendant was adamant that he was innocent.
Enough to meet a specific task or purpose
Though his resume was adequate, the company doubted whether he’d be a good fit.
Enough to suit your needs
Our house isn’t big, but it’s adequate for the two of us.
Close to or next to
The park is adjacent to the school.
Unfavorable; against one’s desires
I had an adverse reaction to my medication and had to stop taking it.
Friendly, easy to talk to
As the most affable of the teachers, Mr. De Soto was the math teacher all the students wanted.
Having several potential meanings; unclear and difficult to understand
When I asked HR what my chances were of getting the job, they gave me a very ambiguous reply.
Having a powerful desire for success or achievement
Kelsey is so ambitious she's settling for nothing less than the presidency.
To destroy or kill
The dictator sent orders to annihilate the group of rebels.
A strong feeling of dislike
Her antipathy toward the professor was obvious: she rolled her eyes whenever he entered the classroom.
Readily seen or understood
Alexis said she was fine, but the tears in her eyes made it apparent she was lying.
Upward movement; advancement
Ruthless and cunning, Mable refused to let anyone come in the way of her ascent to the country's highest political office.
To give credit
Be sure to attribute credit to your sources when writing a research paper.
Based on a whim or random decision
Flipping a coin is an arbitrary way to make a decision.
Requiring a lot of effort
After you cross the bridge, there’s an arduous walk up the hill.
Kind, generous
Many cultures believe in benevolent spirits.
A preconception that prevents objectivity
It’s important to avoid bias when investigating a crime.
To support, strengthen, or fortify
If we work together, we should be able to lift and then bolster the couch.
Growing quickly; flourishing
It didn't take long for my burgeoning cake business to have more customers than I could handle.
To avoid
The longtime cab driver knew the exact backstreet to take in order to bypass the traffic pileup.
Direct, blunt
Josh is candid about his desire to become an actor.
The trait of being honest and frank
I admire her candor, especially when nobody else bothers to speak up.
To use to your advantage
I’d like to capitalize on your math skills by having you work the cash register.
Something that causes a change or new event
Everett's unfair conviction was the catalyst for his lifelong interest in justice and criminal reform.
Unending, without pause
No matter where you were on the island, it was possible to hear the ceaseless sound of the sea.
To express strong disapproval
Every parent in our district censured the education cuts.
To make clear or intelligible
Whenever I'm feeling overwhelmed, I try to take a walk to try to clarify my thoughts and decide what to do next.
To happen at the same time
It wasn’t until after I booked my ticket that I realized the concert coincided with my finals.
Sufficiently qualified
We need to hire a competent web developer to create a good website for our company.
Satisfied, with no desire to change or improve
Though he had never won any awards or even been published, he was complacent with his life as a poet.
To make perfect or complete
This wine perfectly complements this platter of gourmet cheese.
To hide
Bram wore his hat low to conceal the scar on his face.
To agree
Brian believes women should be paid as much as men, and I concur.
To reduce to a shorter form; to make more compact
Rhiannon's boss asked her to condense the 15-page report into a one-page memo.
To limit or restrict; to enclose within bounds
After breaking curfew for the third time, Tony's parents confined him to the house for a month.
A coming together of people or things; a joining
The confluence of hot and cold air created a powerful thunderstorm.
One after another in uninterrupted succession
The robber was ordered to serve his two sentences consecutively, with the shorter sentence being served first.
To give comfort; to lessen grief
Maggie always remembered that Sebastian was the first to console her after her dog died.
A dispute; opposition; rivalry
As they'd been enemies since childhood, Meena expected bitter contention from Jane when she voiced her opinion.
Line or edge that defines the bounds of an object
The winding road followed the contours of the Vosges Mountains.
To be in contrast with
The camera footage contradicts his alibi.
Highly debatable and causing contention
Millions of viewers watched the controversial debate take place.
Abiding by accepted standards
Ebba lives a conventional life in the suburbs.
To pass on or transfer (information)
I have trouble conveying my thoughts in French.
Jiro always takes copious notes during history class.
Friendly; courteous
Because she was the one to break their engagement, Anya was nervous about seeing Eric again, but he was nothing but cordial.
Critical; extremely important
Once General Grant received crucial information about the position of enemy troops, he was able to plan his strategy.
Rudimentary; unrefined
My own painting appeared crude and childlike compared to the prize winner's masterpiece.
Unwieldy; burdensome
The bag of overstuffed pillows was light, but its cumbersome shape made it difficult to carry.
To trick or deceive
My ex-boyfriend deceived me  by pretending to be a millionaire.
Respect; regard
Her deference to the elderly makes her the perfect candidate for an internship at the retirement center.
A lack
Many sailors were stricken by scurvy until it was learned the disease was caused by a Vitamin C deficiency.
To represent
Mama was furious after the caricaturist depicted her with a unibrow and buck teeth.
To overuse over time so that resources become scarce.
The lost campers quickly depleted their supply of food.
Bare, empty
The moon is one giant, desolate landscape.
To deduce; to obtain from a source or origin
Many English words are derived from German.
As he charged, the knight's face was devoid of any fear.
Skill in moving the hands or body; cleverness
The brain surgeon used great dexterity as she made the tiny incision.
To stray from the main topic
I don't mean to digress from your story, but have you seen this new YouTube video?
To shrink or reduce
Sprinkle baking soda on the carpet to diminish red wine stains.
An inconsistency or difference
A discrepancy in her tax returns caused Geraldine to receive half the refund she was owed.
To take apart
To stem rampant corruption, the new CEO dismantled the entire C-suite and hired new managers.
Aunt Lola's distinctive turquoise hair always makes her easy to find in a crowd.
Ruling, controlling; being in a position of authority
The dominant male gorilla is the only one permitted to produce offspring.
Maximizing productivity
Now that I’m following a schedule at work, I’m much more efficient.
To remove
Our team lost the match and was eliminated from the competition.
Superior or distinguished; high in position or status
Our town made news when the eminent magician came to perform at our local theater.
To fully occupy the mind or attention
Lydia was so engrossed in her magazine that she missed her train stop.
To wear away (figuratively or literally)
The constant lies eroded my trust in James.
An approximate value
Try to get an estimate of the number of people attending the concert.
Without beginning or end
Many people who are afraid of dying have searched for the secret to eternal life.
To serve as a superior example of a thing
Mark Twain's writings exemplified the humorist style.
To use up (as in energy or money)
Be careful not to expend all your energy in the first half of a marathon.
To speed the process
You'll need to expedite the shipping if you want the gift to arrive in time for your brother's birthday.
Expert knowledge or skill in a particular skill
The doctor's expertise is in knee surgeries.
To reveal or unmask
The emails sent to the journalist exposed the company's corruption.
Covering a large area; great in number
Ash bought the car for a great price, but its issues were extensive.
Hard to please; taking excessive care
Mrs. Pelton was fastidious and never had so much as a speck of dirt on her clothes.
An imperfection or defect
Alexei was devastated when she discovered an unsightly flaw in the diamond her fiance had given her.
To be unstable; to rise and fall
Stocks can fluctuate on a daily basis, making it difficult to determine when to buy or sell one.
Frantic, frenzied
After three cups of coffee, Wally ran through the house, filled with frenetic energy.
Capable of working or operating
The television looked impressive, but it wouldn't be functional until Dad fixed the wiring problem.
Being awesome or impressive
The Palace of Versailles was designed to show the grandeur of the French court.
Important in history
July 20, 1969, is a historic day: it's the first day men walked on the moon.
Up until now
All attempts to lead into gold have hitherto been unsuccessful.
Harmful, dangerous
The voices around the corner sounded angry, hostile even.
Supposed; related to a hypothesis
For my physics homework, I must come up with a hypothetical situation.
Apathetic, not caring
Anjuli's father was indifferent to her Tik Tok fame.
Huge, vast
Alone in the immense forest, the hiker could see nothing but trees.
About to happen
As the black clouds towered in the sky, Madeleine knew the storm was imminent.
Manuel found it inconceivable that Alfred Hitchcock never won a Best Director Oscar.
Casual, without ceremony
I wasn't expecting the party to be so informal and wished I'd worn sandals instead of heels.
To hinder or prohibit
Keeping the wound clean and covering it with a bandage will inhibit infection.
New or different
The inventor's innovative designs for flying machines stunned his audience.
Complex; having many interrelated parts
It takes Alma at least a week to complete each intricate weaving.
An unorganized mess; confused or muddled
The young boy searched for his homework among the jumbled clutter on his bedroom floor.
Slow; lacking energy
During the languid days of summer, there's nothing I like more than sitting on the porch with a glass of lemonade.
The second of two things
Between sitting at home and going to the beach, I prefer the latter.
Indifferent; having little energy or interest
A nasty bout of the flu left Harry listless and bored.
Capable of making a lot of money; profitable
Writing books isn’t a particularly lucrative career, unless you’re J.K. Rowling.
Harmful, spiteful
The malicious spirit drove out the inhabitants from their home.
Capable of being molded or changed
Children’s minds are malleable but only for so long.
To change, alter, or tweak
Dr. Nguyen modified the gene so that it wouldn’t carry the disease.
Historically significant
Her win in the election was momentous.
New, innovative
We are looking for novel ways to approach the project.
A subtle difference in meaning
Body-language experts even understand the nuances of facial expressions.
Judgment based on observations instead of emotions or opinions
In scientific research, objectivity is of utmost importance.
No longer used; rare or uncommon
Historians assumed record players would be obsolete by now, but in fact they’re making a huge comeback.
Almighty and all powerful
Gods are omnipotent beings who can control human destiny.
An idea that seems contradictory or improbable but is, in fact, true
It always struck Gene as a paradox that standing could be more tiring than walking.
First in importance
Before you start the experiment, it's paramount that you put gloves on.
Preferring one option over others
We can get strawberry ice cream, but I'm actually more partial to chocolate.
Continuous, everlasting
Jackson's perpetual luck meant he died a wealthy and happy man.
To confuse or complicate
Agatha was perplexed by the complicated geometry question.
Believable, worthy of trust
Jan's teacher didn't find it plausible that his dog had eaten his homework.
The potion was potent enough to clear Mark's sinuses immediately.
Genevieve's simple and pragmatic idea solved our problem.
Exact; strictly defined
For baking, more than cooking, you need to be precise with your measurements if you want your recipes to turn out well.
To come before (in time)
The Pyramids of Giza predated Cleopatra by some 2,500 years!
Occurring too soon
Because it was only their second date, Alex thought talk of their future wedding colors was premature.
Foresight, knowing something before it happens
As more of its plot appears to come true in the 21st century, Orwell's 1984 astounds readers with its prescience.
Having a strong reputation; impressive
After saving three children from drowning, Eli was honored with the city's most prestigious award.
Competent or skilled at a thing
Gaia wrote she was "proficient in coding" even though she'd flunked Computers 101 in college.
To forbid or prevent
Because she hated rock music, my strict aunt prohibited me from attending the concert.
Producing great quantities, often frequently
Mr. Johnson is a prolific writer and has published one novel a year for decades.
To make longer in time
Jackie was enjoying herself so much she looked for ways to prolong the date she was on.
Easily noticeable; well-known
Actor Jimmy Durante was known for his gravelly voice and prominent nose.
To project
The hiker was so thin I could see his bones protruding under his skin.
Involving qualities of something (features and content)
I noticed a qualitative change in her paintings.
Involving quantities (numbers and amounts)
We must conduct a quantitative analysis.
Extreme; strikingly different from the traditional form
The politician's views were so radical it was clear she had no shot at winning.
To strengthen or add support to
We can use these pipes to reinforce the structure.
Closely related to the matter at hand
Despite intense interest in her divorce, the movie star ordered the journalist to only ask her questions relevant to her upcoming film.
Determined; set in opinion
I begged Mrs. Jacobi to raise my biology grade, but she was resolute that I'd gotten the grade I deserved.
Contemplation of the past
In retrospect, Jordan realized he was the reason most of his relationships had ended.
To restore to live or consciousness; to activate
Although he was exhausted, a glass of cold water revived James enough that he could finish his story.
To bring about significant change
Instagram revolutionized the travel industry and how people choose which places to visit.
Full of small holes
After the battle, the buildings were riddled with bullet holes. 
Severe or harsh
If Marian wanted to be accepted into the FBI, she knew she'd have to exercise rigorously to pass the fitness test.
To examine carefully and critically
The teacher scrutinized her students’ essays.
To show doubt
Lori insisted she would always do her chores from now on, but her mother was skeptical.
The joining of commonalities or common purposes among a group
I stood in solidarity with other female students by refusing to wear the school’s sexist uniform.
Insufficiently, meagerly, or in a restricted manner
Due to my condition, I must eat salt sparingly.
Showing little or no change
Despite all the diet changes I'd made, my weight remained static.
Loyal, steadfast
Despite his failures, Tim's mother always remained his staunch supporter.
Requiring intense exertion
After getting the flu, I was ordered to avoid strenuous activity from the next two weeks while I recovered.
Coming later or after
Dani ate four pieces of blackberry pie and subsequently got a stomach ache.
Intending to overthrow, deceive, or destroy
Fearing a loss of power, the dictator imprisoned all journalists, claiming their writings were subversive.
Enough; just meeting a requirement
These boxes should be sufficient for our move.
Luxurious; costly
"I've never seen such sumptuous curtains!" Ms. Gala exclaimed as we toured the mansion.
Expressing the same idea
Our brand is synonymous with value and quality which is why we make so many sales.
Jon found washing dishes incredibly tedious; therefore his sink was always overflowing.
Not yet finalized
We haven’t made any official arrangements yet, but the tentative location for our wedding is Hawaii.
Permitting some, but not all light to pass through
The blurry outline of the backyard was just visible through the translucent curtains.
Of little importance or value
Jordan thought the color of shoes I wore was a trivial matter, but he didn't realize how important this party was to me.
Being everywhere at once
Cell phones are ubiquitous these days.
Never before known or experienced
The oceans' temperatures have been rising at an unprecedented rate.
To prove or declare valid
Your selfish actions do not validate your feelings for me.
Ability to be done in a practical or useful way
The viability of the solution is questionable.
Urgently necessary
It is vital that you respond by the deadline.

How Should You Study ACT Vocabulary Words: The Waterfall Method

Anyone hoping to get a high score on the ACT should study using official ACT practice tests. Take these tests timed, and in one sitting, to get the most accurate estimate of how you'd score on the actual ACT. As you go through practice tests and additional practice problems, take note of any words they include that you are unsure of. Add these to your ACT vocab words to study. Similarly, if there are words from the above list that you are confident about, you don't need to spend additional time studying them.

When you have your set of ACT vocabulary words you want to study, we recommend turning them into flashcards. Flashcards are a great way to test yourself on vocab. They don't take long to make, and you can quiz yourself on them again and again until you know all the words. We recommend creating physical flashcards (as opposed to online flashcards) because then you can use our preferred flashcard study method: The Waterfall Method. With this method, you'll get to see all the words in your ACT vocab list, going over the most challenging words more often than the ones you already know or sort of know.

Once you have your list of ACT vocabulary words and your flashcards made, here's how to use the waterfall method:


Once you’ve made your flashcards, split them up into decks (you can put whatever words you want in these decks) of about 30-50 cards each. Choose one deck to be your Starting Stack. 

Go through your Starting Stack, looking at each and every card. For the words you know, put them in a Know It pile. For the words you don’t know, put them in a separate Struggled pile as so:


Now, pick up your Struggled pile and go through each card in it (leave your Know It pile where it is). Put the cards you know in a second Know It pile and the ones you don’t know in a Struggled pile.

You should now have two Know It piles and one Struggled pile:


Repeat this process of picking up your Struggled pile and going through each card until you’re left with about one to five cards in your Struggled pile:


By now you should know most, if not all, cards in your deck. But it isn’t enough to just go through them once—you also have to work back up your “waterfall” of cards. 

To do this, combine your Struggled pile with your last Know It pile (the pile closest to the Struggled pile). This will be your Working pile. Go through all the cards in this pile. If there are any words you forgot, go through the entire pile of ACT vocab flashcards again and again until you've learned all the definitions in it.


Continue this pattern by combining your current Working pile with the next Know It pile. Go through all these cards until you know each one.


At the end, you should have made your way all the back to your original Starting Stack. You now know all the ACT words and their meanings in your deck! Repeat this waterfall method with the other decks you make so that you can learn even more critical ACT test vocabulary.


What's Next?

Practice tests are one of the best ways to prepare for the ACT. We have links to every free and official ACT available, so you can get started with your studying!

Not sure when to take the ACT? Get a complete study plan for the ACT to figure out the best date for you.

Taken the ACT already but unhappy with your score? Use our guide to decide whether you should retake the ACT.


Want to improve your ACT score by 4 points?

Check out our best-in-class online ACT prep program. We guarantee your money back if you don't improve your ACT score by 4 points or more.

Our program is entirely online, and it customizes your prep program to your strengths and weaknesses. We also have expert instructors who can grade every one of your practice ACT essays, giving feedback on how to improve your score.

Check out our 5-day free trial:

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Christine Sarikas
About the Author

Christine graduated from Michigan State University with degrees in Environmental Biology and Geography and received her Master's from Duke University. In high school she scored in the 99th percentile on the SAT and was named a National Merit Finalist. She has taught English and biology in several countries.

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