/ˈæk.tə/
noun
A person who performs, plays a part in a theatrical play or film.One who acts; a doer.One who takes part in a situation.An advocate or proctor in civil courts or causes.One who institutes a suit; plaintiff or complainant.(policy debate) One who enacts a certain policy action.The entity that performs a role (in use case analysis).(grammar) The most agent-like argument of a clause, e.g. 'the torpedo' in "The torpedo sank the boat" and "The torpedo fired".