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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Lloyd's said on Wednesday that it first received "certain whistleblowing reports" in November 2023 but that it didn't act on them.
From BBC ● Jul. 22, 2026
“The Commission found that streaming platforms offering children’s content will continue to act as a competitive constraint on the merged entity’s TV channels,” the agency said.
From Los Angeles Times ● Jul. 22, 2026
The board is supposed to act independently but the lawsuit alleges that Mamdani influenced the outcome.
From The Wall Street Journal ● Jul. 22, 2026
The researchers also propose that heavy noble gases in lunar soil could act as "fossil records" of earlier interactions between the solar wind and Earth's magnetosphere.
From Science Daily ● Jul. 21, 2026
But before he could act, before he could react, something unexpected happened.
From "Chronicles of a Lizard Nobody" by Patrick Ness
That year, a faculty committee produced hundreds of pages of analysis that ultimately recommended UC continue using the SAT and ACT in admissions.
From Los Angeles Times ● Jul. 13, 2026
The debate comes as UC increasingly stands as a national outlier in its refusal to consider SAT and ACT scores.
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
After Dad went to bed, Richard told me that he’d taken a practice test for the ACT.
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
"We have the licensing act. It was created quite a long time ago and it hasn't kept up with the reality on the ground," he says.
From BBC ● May 10, 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
“Every student can only appear in one act. Dr. Throckmorton doesn’t want anybody trying to impress the Excelsior judges by appearing onstage two or three different times.”
From "Shine!" by J.J. and Chris Grabenstein
In this case, each cancer treatment acts as an environmental pressure.
From Science Daily ● Jul. 22, 2026
That jet stream acts as a giant conveyor belt, bringing storms and rain to the Southern U.S. — but that El Niño conveyor belt doesn’t typically reach northern states.
From Los Angeles Times ● Jul. 22, 2026
Be wary of any market expert who acts too confidently about what they can deliver.
From MarketWatch ● Jul. 21, 2026
Policies to give people more "breathing space" on the cost of living will be announced on Tuesday by Andy Burnham, in one of his first acts as prime minister.
From BBC ● Jul. 20, 2026
He could use his writing to inspire acts of patriotism and bravery.
From "A Thousand Sisters" by Elizabeth Wein
The FA said it is "alleged that the head coach acted in an improper manner and/or brought the game into disrepute by directing and/or authorising the observation of training sessions" of these games.
From BBC ● Jul. 22, 2026
If state regulators agree it acted reasonably, Edison will be reimbursed for payments it makes to victims by a $21 billion wildfire fund, which Newsom created through legislation in 2019.
From Los Angeles Times ● Jul. 21, 2026
"We believe public health is a shared responsibility among restaurants, their suppliers, and authorities, and we are proud to have consistently acted quickly and proactively to protect our guests."
From Barron's ● Jul. 17, 2026
Phosphate, an essential nutrient for marine life, acted as a hidden regulator of Earth's carbon cycle for the last 60 million years, although its exact role had not been fully understood.
From Science Daily ● Jul. 16, 2026
As she did, details in the trunk became clearer, until she realized it wasn’t a single huge tree, but dozens of smaller trees that grew so close together, they acted as one.
From Anya and the Nightingale by Sofiya Pasternack
Looking back on his early years, Damon recalled traveling to New York with his childhood friend and fellow actor, Ben Affleck, in hopes of landing acting jobs.
From MarketWatch ● Jul. 22, 2026
The district has not released his contract, but his salary as acting superintendent was about $396,000 a year.
From Los Angeles Times ● Jul. 21, 2026
Nearly 500 Panamanian vessels were detained for inspection in 2026, according to local media reports, but acting Foreign Minister Carlos Hoyos said Monday that those numbers have now returned "to the historical level."
From Barron's ● Jul. 21, 2026
“Brett is an incredibly talented economist who is meticulous and who takes a holistic approach to the BLS data,” said Pierre Yared, who stepped down as acting chairman of the CEA earlier this summer.
From The Wall Street Journal ● Jul. 20, 2026
For a moment, Jonah was afraid that she wasn’t going to react—why was she acting so freaky?
From "Found" by Margaret Peterson Haddix
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.