ph.

1. 运作不正常；出毛病
If something is acting up, it is not working properly.

2. （孩子）耍脾气，捣蛋
If a child is acting up, they are behaving badly.

1. make itself felt as a recurring pain

e.g. My arthritis is acting up again

2. misbehave badly
act in a silly or improper way

e.g. The children acted up when they were not bored

Synonym: carry on