- 1(Of a thing) fail to function properly: the plane’s engine was acting upMore example sentences
malfunction, go wrong, be defective, be faulty• informal be on the blink, be on the fritz
- The laptop computer that we have been using for performing pulmonary function tests had been acting up lately, overheating and shutting itself off.
- Then again, my body did like to pick the wrong times to start acting up.
- I think the service is messed up here, it was acting up before the phone broke.
More definitions of act upDefinition of act up in:
- The British & World English dictionary