act something ↔ out phrasal verb (see also act)

1. if a group of people act out an event, they show how it happened by pretending to be the people who were involved in it:
The children were acting out the story of the birth of Jesus.

2. to express your feelings about something through your behaviour or actions, especially when you have been feeling angry or nervous:
These teenagers are likely to act out their distress by running away.

[TahlilGaran] Dictionary of Contemporary English ▲

act out
to behave badly because you are unhappy or upset.
These kids are very angry and act out because their lives are a mess.

Etymology: based on the idea of acting out a story (= telling a story through physical actions)

[TahlilGaran] English Idioms Dictionary ▲

act out
v.
1. To show an idea, story, or happening by your looks, talk, and movements.
He tried to act out a story that he had read.
2. To put into action.
All his life he tried to act out his beliefs.

[TahlilGaran] English Idioms Dictionary ▲