Definition
When an individual, particularly a child, misbehaves or causes trouble.
（尤指孩子）調皮，搗蛋
The little boy kept acting up in class, which really frustrated the teacher.
那個小男孩在課堂上不斷搗亂，這讓老師非常沮喪。
He always acts up at home, leaving his parents feeling overwhelmed.
他在家裡總是搗亂，讓他的父母感到不知所措。
The children acted up in the store, making other shoppers uncomfortable.
孩子們在商店裡搗亂，讓其他顧客感到不舒服。
When a machine or part of the body fails to function properly or encounters issues.
（機器）出故障；（身體）不舒服
This printer has been acting up lately, constantly jamming.
這台印表機最近一直在出問題，經常卡紙。
I feel like my knee is acting up; it hurts when I walk.
我覺得我的膝蓋出問題了，走路時會痛。
The television is acting up today and seems to have some issues.
電視今天出問題了，似乎有些故障。