(intransitive) To do something. / (obsolete, transitive) To do (something); to perform. / (intransitive) To perform a theatrical role. / (intransitive) Of a play: to be acted out (well or badly).

(countable) Something done, a deed. / (obsolete, uncountable) Actuality. / (theology) Something done once and for all, as distinguished from a work.

Ellipsis of Act of Parliament.

(idiomatic) In the process of doing something considered criminal or otherwise wrong; used to emphasize the eye-witness evidence.

Abbreviation of activities. / Abbreviation of actor. / Abbreviation of actuary.

Abbreviation of acting. / (grammar) Abbreviation of active. / Abbreviation of actual.

To act decisively on the basis of information received or deduced. / Το act accordingly to a (usually sublimated) desire or impulse. / To take action against something. / (medicine) To affect something.

Abbreviation of Acts.

An instance of a certain standardized college admissions test in the United States, originally called the American College Test.

Initialism of Australian Capital Territory, a federal territory of Australia. / Initialism of American College Test.