What does "act up" mean?

To misbehave; to cause trouble.

What is a synonym for "act up"?

Common synonyms include: carry, carry on, cut up, horse, horse around, play.

/ækt ˈʌp/ verb

verb ·Rare ·Advanced level

Verb

1
To misbehave; to cause trouble. idiomatic, intransitive
"My allergies act up during hay fever season."
2
make itself felt as a recurring pain wordnet
3
To perform the duties of an appointment senior to that actually held; to deputise for a superior. idiomatic, intransitive
"Acting up is always recommended when you find yourself under a new boss."
4
misbehave badly; act in a silly or improper way wordnet

"My allergies act up during hay fever season."