What is the meaning of Acting?

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

present participle and gerund of act

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.

to act up; to temporarily assume duties or authorities of another person when they are unable to do their job

Source: wiktionary.org