act up — not work properly
phrasal verbB2IELTS 6+informalcommon
to stop working correctly or cause problems, especially for machines, devices, or body parts.
Say it like a native
Textbook My laptop has been malfunctioning intermittently all week.
Native My laptop's been acting up all week.
'Act up' is the casual way to say a device or body part is playing up; 'malfunctioning intermittently' is technical.
Pattern: subject + act up
In use
- My laptop started acting up right before my online meeting.technology
- Sometimes, my internet connection acts up during important video calls, which can be very frustrating.IELTS speaking
Common mistake
✗ My back has been acting out lately.
✓ My back has been acting up lately.
It's 'act UP' (playing up); 'act out' means express feelings through bad behaviour — a different thing.
Common collocations
act up (device/body part)— my knee, the engine, the wifi, again
Don't confuse it
Don't confuse with 'break down', which usually means something stops working completely.
Related
- act up (misbehave) — Another meaning of 'act up' is 'misbehave'; compare the examples to keep the meanings separate.