The stirring music acted on the emotions of the audience.
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.
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 Englishact(e) (< Middle French) < Latinācta, 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 < Latināctus a doing (āg- + -tus suffix of v. action)
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.