anything done, being done, or to be done; deed; performance.
a heroic act.
the process of doing.
caught in the act.
a formal decision, law, or the like, by a legislature, ruler, court, or other authority; decree or edict; statute; judgment, resolve, or award.
an act of Congress.
an instrument or document stating something done or transacted.
one of the main divisions of a play or opera.
the second act of Hamlet.
a short performance by one or more entertainers, usually part of a variety show or radio or television program.
the personnel of such a group.
The act broke up after 30 years.
The politician's pious remarks were all an act.
Philosophy. (in scholasticism)
activity in process; operation.
the principle or power of operation.
form as determining essence.
a state of realization, as opposed to potentiality.
to do something; exert energy or force; be employed or operative.
He acted promptly in the emergency.
to reach, make, or issue a decision on some matter.
I am required to act before noon tomorrow.
to operate or function in a particular way; perform specific duties or functions.
to act as manager.
to produce an effect; perform a function.
The medicine failed to act.
to behave or conduct oneself in a particular fashion.
to act well under all conditions.
to pretend; feign.
Act interested even if you're bored.
to perform as an actor.
He acted in three plays by Molière.
to be capable of being performed.
His plays don't act well.
to serve or substitute (usually followed byfor ).
In my absence the assistant manager will act for me.
to represent (a fictitious or historical character) with one's person.
to act Macbeth.
to feign; counterfeit.
to act outraged virtue.
to behave as.
He acted the fool.
Obsolete. to actuate.
act up
to fail to function properly; malfunction.
The vacuum cleaner is acting up again.
to behave willfully.
The children always act up in school the day before a holiday.
to become painful or troublesome, especially after a period of improvement or remission.
My arthritis is acting up again this morning.
get / have one's act together to organize one's time, job, resources, etc., so as to function efficiently.
The new administration is still getting its act together.
act on / upon
act out
to demonstrate or illustrate by pantomime or by words and gestures.
The party guests acted out stories for one another.
Psychology. to give overt expression to (repressed emotions or impulses) without insightful understanding.
The patients acted out early traumas by getting angry with the analyst.
act one's age, to behave in a manner appropriate to one's maturity.
We children enjoyed our uncle because he didn't always act his age.
clean up one's act, to begin adhering to more acceptable practices, rules of behavior, etc..
The factory must clean up its act and treat its employees better.
act funny, to display eccentric or suspicious behavior.
Trademark. a standardized college admissions test developed by ACT, Inc., measuring English, mathematics, reading, and science skills: originally an abbreviation of American College Testing/American College Test.
Association of Classroom Teachers.
Australian Capital Territory.
acting.
active.
actor.
actual.
something done or performed; a deed
the performance of some physical or mental process; action
(capital when part of a name) the formally codified result of deliberation by a legislative body; a law, edict, decree, statute, etc
(often plural) a formal written record of transactions, proceedings, etc, as of a society, committee, or legislative body
a major division of a dramatic work
a short performance of skill, a comic sketch, dance, etc, esp one that is part of a programme of light entertainment
those giving such a performance
an assumed attitude or pose, esp one intended to impress
philosophy an occurrence effected by the volition of a human agent, usually opposed at least as regards its explanation to one which is causally determined Compare event
(intr) to do something; carry out an action
(intr) to function in a specified way; operate; react
his mind acted quickly
to perform (a part or role) in a play, etc
(tr) to present (a play, etc) on stage
(intr; usually foll by for or as) to be a substitute (for); function in place (of)
to serve the function or purpose (of)
the glass acted as protection
(intr) to conduct oneself or behave (as if one were)
she usually acts like a lady
(intr) to behave in an unnatural or affected way
(copula) to pose as; play the part of
to act the fool
(copula) to behave in a manner appropriate to (esp in the phrase act one's age )
not_standard (copula) to seem or pretend to be
to act tired
to start to behave in a responsible manner
informal to become involved in a profitable undertaking or advantageous situation in order to share in the benefits
informal to become organized or prepared
Australian Capital Territory
(formerly in Britain) advance corporation tax
See action.
First recorded in 1350–1400; Middle English act(e), from Middle French, from Latin ācta, plural of āctum “something done,” noun use of neuter past participle of agere “to do, drive”; also from Latin āctus “deed,” noun use of masculine past participle of agere
When you do something, you act. A commercial that says "Act now!" means "Get up from the couch and order me! This minute!" Act is both a noun and a verb. You can perform an act of kindness or violence. Or, you can act in a play. People who take on roles and perform them are actors. Likewise, plays, operas, and ballets are broken down into acts. You may have seen references to Shakespeare's plays, such as "Act I, Scene IV." Comedians refer to their shows as acts. Other performers, from magicians to lion tamers, sometimes do the same: a magic act is a magician's show.
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Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
What’s inevitably lost is the excitement of watching a single performer act the chameleon, flipping between characters as if changing psychic TV channels.
From The Wall Street Journal ● Jul. 14, 2026
Jennifer Finch, the bassist for veteran LA rock act L7, has brain cancer and will not perform with the band on its farewell tour this year.
From Los Angeles Times ● Jul. 14, 2026
"We must act now to turn this transformation into an opportunity," she added.
From Barron's ● Jul. 14, 2026
A little background on ethics: Not all money managers are fiduciaries — professionals who have to act in their client’s best interest under the Investment Advisers Act of 1940.
From MarketWatch ● Jul. 14, 2026
“Don’t you dare sit there and act like you were mother of the year,” he says bitterly.
From "Split the Sky" by Marie Arnold
Most speakers were science, technology, engineering and math, or STEM, professors who urged the board to bring back the SAT and ACT.
From Los Angeles Times ● Jul. 14, 2026
There are early signs that views may have changed in the six years since the governing board unanimously voted to eliminate SAT and ACT requirements.
From Los Angeles Times ● Jul. 9, 2026
McClure, from the ACT party, said the travel ban was "a type of foreign interference" and that she was "not going to apologise for visiting Taiwan", the New Zealand Herald reported.
From BBC ● Jun. 4, 2026
After a pandemic-era push to stop requiring standardized tests like the SAT and ACT, some schools are bringing them back.
From The Wall Street Journal ● Jun. 3, 2026
I was worried: Dad’s expectations were so high, and Richard’s fear of disappointing him so intense, it seemed possible that Richard might not take the ACT at all.
From "Educated" by Tara Westover
“We know who they are and how they act. So we will be prepared.”
From The Wall Street Journal ● May 28, 2026
But during her sentencing ruling Olivier said "it wasn't... an impulsive act. It was the event of the evening," the AFP news agency reports.
From BBC ● Apr. 16, 2026
“The pause highlights a balancing act. Officials have moved away from peak restriction,” analysts at U.S.
From MarketWatch ● Mar. 31, 2026
"Eastern Africa is on the front line of change, but there is still time to act. Smarter land management -- like conserving forests and restoring vegetation -- can protect rainfall and sustain agricultural growth."
From Science Daily ● Dec. 12, 2025
“That’s not any of my business, Jason. If you had any actual proof, I’d have to act. But without that I dont figger it’s any of my business.”
From "The Sound and the Fury" by William Faulkner
This acts like an envelope and all the researchers need to do is change the letter inside before posting it into the body.
From BBC ● Jul. 13, 2026
The regional police force initially leading the investigation, Devon and Cornwall Police, said Monday that a suspect arrested earlier had been "re-arrested on suspicion of commission, preparation or instigation of acts of terrorism".
From Barron's ● Jul. 13, 2026
On Monday, counterterrorism police said the same man was rearrested on suspicion of “commission, preparation or instigation of acts of terrorism” after new evidence had come to light.
From The Wall Street Journal ● Jul. 13, 2026
"We also found that DT-109 primarily acts in the gastrointestinal tract, but its reach stretches much further."
From Science Daily ● Jul. 11, 2026
After school on Friday, everyone is scurrying off to different rooms and rehearsal spaces to work on their acts for the talent show.
From "Shine!" by J.J. and Chris Grabenstein
In the old investment paradigm, government bonds acted as shock absorbers, with prices rising and yields falling when the economy takes a hit.
From The Wall Street Journal ● Jul. 12, 2026
When Social Security came close to running out of money in the early 1980s, Congress acted — at the 11th hour.
From MarketWatch ● Jul. 11, 2026
I just loved how she expressed herself with what she wore and how she acted.
From Los Angeles Times ● Jul. 10, 2026
The Queen, also a self-confessed Archers addict, acted out her role as president of the National Osteoporosis Society, in a special episode to mark The Archers' 60th anniversary.
From BBC ● Jul. 9, 2026
The dragon’s claws acted like ramparts, perfect for defense.
From "Half Upon a Time" by James Riley
He recommended I take acting classes at the William Esper Studio in Manhattan.
From The Wall Street Journal ● Jul. 14, 2026
It’s shaping up to be a rough week for acting Attorney General Todd Blanche.
From Slate ● Jul. 14, 2026
As well as being a good cultural and financial fit, you also want to make sure he is acting in your best interest.
From MarketWatch ● Jul. 14, 2026
"We're building a proving ground for Moon Base operations," said Ryan Stephan, NASA's Moon Base acting director of cargo landers.
From Science Daily ● Jul. 14, 2026
By means of bribery and persuasion and threats, Madame Babushkinov had finally convinced her to stop acting like a coward and get out of bed.
From "The Long-Lost Home" by Maryrose Wood
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
