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

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

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

Abbreviation of Acts.

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

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

Ellipsis of Act of Parliament.

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

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.

to behave in a certain way