- (intransitive) & (linking) If you act in some way, you do something that makes people think you are that way.
- When he must do something, he acts quickly.
- Don't do anything strange. Just act normal.
- She acted the fool when she saw him.
- (transitive & intransitive) If you act, you perform in a film or a play.
- Daniel Radcliffe acts in the Harry Potter films.
- (countable) Something done, a deed.
- Going into the house on fire to help a child was a brave act.
- (countable) An act is a law made by the government.
- The UK's Freedom of Information Act was passed in 2004. It lets people ask questions of the government.
- (countable) An act is when you do something to make people believe something other than the truth.
- Susan seems nice, but it's all an act.
- (countable) An act is a part of a play, opera, ballet, musical, film, or other theatrical piece. An act is sometimes divided into scenes.
- The curtain comes down at the end of each act.