Definition of act up in English:

act up

phrasal verb

  • 1informal (of a thing) fail to function properly.

    ‘the plane's engine was acting up’
    • ‘My modem is acting up so it took forever to log on, shades of things to come.’
    • ‘My leg was acting up, painful and disobedient, but no more than it has a hundred times before.’
    • ‘‘The gearbox started acting up real early in the race, and we didn't think that we would make it,’ said Macaluso.’
    • ‘The laptop computer that we have been using for performing pulmonary function tests had been acting up lately, overheating and shutting itself off.’
    • ‘A couple of weeks ago it started acting up: even after leaving it all night to charge, it sometimes doesn't charge at all.’
    • ‘Then again, my body did like to pick the wrong times to start acting up.’
    • ‘Her right knee was acting up a bit from soccer the day before, and besides, she just didn't feel like it.’
    • ‘Their Internet connection is acting up, so I mucked about and deduced that either Shaw is having issues or stranger things are afoot, then promptly fell asleep.’
    • ‘I think the service is messed up here, it was acting up before the phone broke.’
    • ‘Later I learned that he had thought I was having a problem with the gauge, which had been acting up a few weeks earlier.’
    • ‘My PC has been acting up badly for the past month.’
    • ‘The back still acts up now and again, but the diet at least makes it possible to swing the club - and he has lost 20 lb in weight.’
    • ‘I reckon I covered a mile before my legs started to act up.’
    • ‘But the record player, which has been acting up for months now, wheezed a few breaths before officially dying.’
    • ‘Alas, the desktop computer which was acting up before I'd left has now failed again.’
    • ‘A few weeks back I mentioned that the gear box in the car was acting up a bit, earlier today it went kaput.’
    • ‘No point in fighting it, though I do think it strange that both this and the preceding two monitors started acting up within a couple of months of the end of the guarantee.’
    • ‘I don't think psychologists have to deal with their own computers when they start to act up.’
    • ‘Fortunately I had cut a new CD-Rom backup only the day before the system started acting up so all is not lost.’
    • ‘For instance, this morning I wanted to print some details for Mike and Joan's travel insurance and the printer started to act up, Grrrrrrrrrrrrrr.’
    malfunction, crash, develop a fault, go wrong, break down, give out, stall, be defective, be faulty, fail, cease to function, cease to work, stop working
    View synonyms
    1. 1.1 Behave badly.
      ‘all children talk back and act up from time to time’
      • ‘They're all fab and they tell me when I'm acting up, and laugh at me as much as possible which, I think, is very important and very British.’
      • ‘Lloyd said a dip in quality of teaching meant some well-behaved primary school pupils began to act up in the first year at their comprehensive.’
      • ‘The pupils said the boy was known for his disruptive behaviour and had been acting up in the lesson that day.’
      • ‘The French fish fight hard and don't stop acting up once they're out of the water.’
      • ‘Here's what she should do: every time one of the little blighters starts acting up, simply threaten to show them one of his movies.’
      • ‘If the hoodie gangs go elsewhere and act up, that's not their problem - indeed, if the shopping centre becomes safer than the average High street, it might even make them more money.’
      • ‘What's sad, is that I felt embarrassed: I was obviously very disturbed, was acting up at school and needed counselling, yet the stigma of seeing a child psychiatrist was hard to bear.’
      • ‘The little feller's been acting up a bit lately; pounding up and down while making lengthy speeches and various other odd things.’
      • ‘The day we visit the kindergarten is only the second time in his life that Ed acts up.’
      • ‘Eventually, Peter moves into the house too, also shared by a slightly loopy spinster, Miss Byron, and the pair feel free to reject society's expectations by acting up.’
      • ‘As usual, Mac was acting up, arguing about line-calls and holding up play as he ranted at the umpire.’
      • ‘Patsy said: ‘They can feel quite isolated and often the pupils act up more with an unfamiliar teacher.’’
      • ‘She really toughened up and started bunking off school and acting up.’
      • ‘The head of the school says the children were encouraged to act up for the cameras.’
      • ‘So at school I used to act up and get into trouble, and then I'd go home to my mum and start crying because I thought the teacher didn't like me.’
      • ‘The teenager was asked about conversations he had with the dean at Los Angeles' John Burroughs Middle School, where the boy had a history of acting up in class.’
      • ‘I was polite, and I pleased my demanding grandmother, I never acted up, I wore dresses, and was the best girl anyone could hope for.’
      • ‘In his three-year-old debut at Gulfstream in January, Friends Lake acted up at the gate and ran badly in the Holy Bull, finishing third, 12 lengths behind the winner.’
      • ‘Last year she started smelling pretty bad and acting up so Mum made her sleep outside in the wood shed during the summer.’
      • ‘A boy is sent out of class for acting up: he resists with all his might the idea that he should conclude it is better not to act up.’
      misbehave, give someone trouble, cause someone trouble, act badly, get up to mischief, get up to no good, be bad, be naughty, forget oneself, misconduct oneself
      View synonyms
  • 2Be promoted to a more senior position on a temporary basis.

    • ‘To the extent that he had greater experience that was because he had been allowed to act up on the retirement of Ms Herman.’
    • ‘One junior officer admitted to acting up as Watch Manager in charge of his station - two ranks above his actual level - on 14 occasions.’
    • ‘As reported last month, the unofficial action involves firefighters across London refusing to act up as officers.’
    • ‘What is the process for being put forward for promotion or acting up; your line manager can do it, or somebody you work with can do it, but somebody else has a final say?’
    • ‘To this Mr Howat is prepared, in deference to the inclusion of ‘deputies’ in the memorandum, to add officers acting up in the rank of superintendent, but no more.’
    • ‘When someone is acting up it takes another uniform off the street,’ he said.’
    • ‘So there is, for example, no acting up to cover for unfilled posts.’
    • ‘He said: ‘There have been problems due to some staff being unwilling to act up.’’