What does "act up" mean?

To behave badly or malfunction When machines or people misbehave or cause problems.

How do you use "act up" in a sentence?

My computer is acting up again. The kids are acting up. My knee acts up in rain.

Phrasal Verb BritishAmericanAustralian ★★★★☆ Common Casual

Meaning: To behave badly or malfunction

出毛病、捣蛋

Funcionar mal o portarse mal

調子が悪くなる、いたずらをする

말썽을 부리다, 오작동하다

When machines or people misbehave or cause problems.

机器出故障或人调皮捣蛋、惹麻烦。

Cuando máquinas o personas se portan mal o causan problemas.

機械が故障したり、人が問題行動を起こしたりすること。

기계가 오작동하거나 사람이 말썽을 부리는 것.

Base verb: act

Particle: up

Separable: No — the verb and particle stay together

My computer is acting up again.
我的电脑又出毛病了
Mi ordenador está fallando otra vez
パソコンがまた調子悪い
컴퓨터가 또 말썽이다.
The kids are acting up.
孩子们在捣蛋
Los niños se están portando mal
子供たちがいたずらしている
아이들이 말썽을 부리고 있다.
My knee acts up in rain.
下雨天膝盖就犯毛病
La rodilla me da problemas cuando llueve
雨の日は膝の調子が悪くなる
비 오는 날에는 무릎이 말썽이다.

Context: malfunction, behavior

Tone: frustrated

From theatrical acting out.

Era: Modern

Generation: All ages

Social background: Universal