Meaning

• To do something.

  "If you don't act soon, you will be in trouble."

• To do (something); to perform.

• To perform a theatrical role.

  "I started acting at the age of eleven in my local theatre."

• Of a play: to be acted out (well or badly).

• To behave in a certain manner for an indefinite length of time.

  "A dog which acts aggressively is likely to bite."

• To convey an appearance of being.

  "He acted unconcerned so the others wouldn't worry."

• To do something that causes a change binding on the doer.

  "act on behalf of John"

• (construed with on or upon) To have an effect (on).

  "Gravitational force acts on heavy bodies."

• To play (a role).

  "He's been acting Shakespearean leads since he was twelve."

• To feign.

  "He acted the angry parent, but was secretly amused."

• (construed with on or upon, of a group) To map via a homomorphism to a group of automorphisms (of).

  "This group acts on the circle, so it can't be left-orderable!"

• To move to action; to actuate; to animate.

Meaning

• An action or deed.

• Something done by a party — so called to avoid confusion with the legal senses of deed and action.

• Pretending.

• The occupation of an actor.

Meaning

• Temporarily assuming the duties or authority of another person when they are unable to do their job.

  "Acting President of the United States is a temporary office in the government of the United States."