1.AdjectiveTemporarily assuming the duties or authority of another person when they are unable to do their job.
"The Acting Minister must sign Executive Council documents in a Minister's absence.; The CEO is currently in a hospital. The CFO is acting CEO in the meantime."
2.Verbpresent participle and gerund of act
3.NounAn action or deed.
4.NounSomething done by a party—so called to avoid confusion with the legal senses of deed and action.