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English definition of “act up”

act up

phrasal verb with act     /ækt/ verb
If a person , especially a child , acts up, they behave badly : Sophie got bored and started acting up.Bad and wrong behaviourDisobedientObeying and breaking the lawObedient and compliant If a machine or part of the body acts up, it does not perform as well as it should: My car always acts up in cold weather . Her shoulder was acting up (= hurting because of injury ).Not functioningPain and painful
(Definition of act up from the Cambridge Advanced Learner's Dictionary & Thesaurus © Cambridge University Press)
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