serving temporarily, especially as a substitute during another's absence; not permanent; temporary: the acting mayor.
designed, adapted, or suitable for stage performance.
provided with detailed stage directions for the performer: an acting version of a play.
the art, profession, or activity of those who perform in stage plays, motion pictures, etc.

1595–1605; act + -ing2, -ing1

proacting, adjective
unacting, adjective

1. provisional, interim. Unabridged


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.
false show; pretense; feint: The politician's pious remarks were all an act.
activity in process; operation.
the principle or power of operation.
form as determining essence.
a state of realization, as opposed to potentiality.
verb (used without object)
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 by for ): In my absence the assistant manager will act for me.
verb (used with object)
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.
Verb phrases
act on/upon,
to act in accordance with; follow: He acted on my advice.
to have an effect on; affect: The stirring music acted on the emotions of the audience.
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 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, Informal. to organize one's time, job, resources, etc., so as to function efficiently: The new administration is still getting its act together.
act funny, to display eccentric or suspicious behavior.
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, Informal. to begin adhering to more acceptable practices, rules of behavior, etc.: The factory must clean up its act and treat its employees better.

1350–1400; Middle English act(e) (< Middle French) < Latin ācta, plural of āctum something done, noun use of past participle of agere to do (āg- past participle stem + -tum neuter past participle suffix); and directly < Latin āctus a doing (āg- + -tus suffix of v. action)

misact, verb (used without object)
postact, noun
preact, verb (used with object)
unacted, adjective
well-acted, adjective

acts, ask, axe.

1. feat, exploit; achievement; transaction; accomplishment. See action. 4. record. 6. turn, routine. 23–13. perform, function, work. 15, 16. play. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
Cite This Source Link To acting
World English Dictionary
act (ækt)
1.  something done or performed; a deed
2.  the performance of some physical or mental process; action
3.  (capital when part of a name) the formally codified result of deliberation by a legislative body; a law, edict, decree, statute, etc
4.  (often plural) a formal written record of transactions, proceedings, etc, as of a society, committee, or legislative body
5.  a major division of a dramatic work
6.  a.  a short performance of skill, a comic sketch, dance, etc, esp one that is part of a programme of light entertainment
 b.  those giving such a performance
7.  an assumed attitude or pose, esp one intended to impress
8.  philosophy Compare event an occurrence effected by the volition of a human agent, usually opposed at least as regards its explanation to one which is causally determined
vb (foll by as)
9.  (intr) to do something; carry out an action
10.  (intr) to function in a specified way; operate; react: his mind acted quickly
11.  to perform (a part or role) in a play, etc
12.  (tr) to present (a play, etc) on stage
13.  (intr; usually foll by for or as) to be a substitute (for); function in place (of)
14.  to serve the function or purpose (of): the glass acted as protection
15.  (intr) to conduct oneself or behave (as if one were): she usually acts like a lady
16.  (intr) to behave in an unnatural or affected way
17.  (copula) to pose as; play the part of: to act the fool
18.  (copula) to behave in a manner appropriate to (esp in the phrase act one's age)
19.  not standard (copula) to seem or pretend to be: to act tired
20.  clean up one's act to start to behave in a responsible manner
21.  informal get in on the act to become involved in a profitable undertaking or advantageous situation in order to share in the benefits
22.  informal get one's act together to become organized or prepared
[C14: from Latin actus a doing, performance, and actum a thing done, from the past participle of agere to do]

abbreviation for
1.  Australian Capital Territory
2.  (formerly in Britain) advance corporation tax

ACT2 (ækt)
n acronym for
(in New Zealand) Association of Consumers and Taxpayers: a small political party of the right

acting (ˈæktɪŋ)
1.  taking on duties temporarily, esp as a substitute for another: the acting president
2.  operating or functioning: an acting order
3.  intended for stage performance; provided with directions for actors: an acting version of ``Hedda Gabler''
4.  the art or profession of an actor

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
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Word Origin & History

late 14c., from O.Fr. acte, from L. actus "a doing" and actum "a thing done," both from agere "to do, set in motion, drive, urge, chase, stir up," from PIE root *ag- "to drive, draw out or forth, move" (cf. Gk. agein "to lead, guide, drive, carry off," agon "assembly, contest in the games," agogos "leader;"
Skt. ajati "drives," ajirah "moving, active;" O.N. aka "to drive;" M.Ir. ag "battle"). Theatrical (1510s) and legislative (mid-15c.) senses of the word also were in Latin. The verb is first attested late 15c.; in the theatrical performance sense it is from 1590s. In the act "in the process" is from 1590s, originally from the 16c. sense of the act as "sexual intercourse." Act of God "uncontrollable natural force" first recorded 1882. To act out "behave anti-socially" (1974) is from psychiatric sense of "expressing one's unconscious impulses or desires."

1590s, verbal noun or prp. adj. from act (q.v.); acting out in psychology is from 1945.
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Abbreviations & Acronyms
  1. a trademark for a standardized college entrance examinationoriginally American College Test

  2. American Conservatory Theater

  3. Waco Regional Airport

The American Heritage® Abbreviations Dictionary, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
Cite This Source
Example sentences
All those circles around the pots and acting as a decorative mulch are pressure
  gaskets and seals from industry machinery.
Then she began walking across the face of the comb, acting confused in the
  bright daylight.
But that does not hold true if the group is itself acting selfishly and so
  exposing us to external threat or harm.
One concept not encountered on these premises is that of gravity acting on
  photons from a position ahead of the photon.
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