act up If a child is acting up, they are behaving badly. 如果一个小孩子act up,那就是说他表现的很差，故意捣乱的意思。 I could hear Jonathan acting up downstairs. 我能听见乔纳森在楼下撒泼。 If you act up in class, you will be sent to the principal's office. 如果你在课堂上