Meaning of ACT UP in English

ACT UP

1.

If something is acting up , it is not working properly. ( INFORMAL )

She was messing with the coffee pot, which was acting up again.

= play up

PHRASAL VERB : usu cont , V P

2.

If a child is acting up , they are behaving badly. ( INFORMAL )

= play up

PHRASAL VERB : usu cont

Collins COBUILD Advanced Learner's English Dictionary.      Английский словарь Коллинз COBUILD для изучающих язык на продвинутом уровне.