(to) Act at one's age

It means to behave in a more mature way. Frequently it would be said to a child or teen.

For example: "Bill, stop throwing rocks! Act your age!.

Tom is a big boy already but never acts his age.

 

这个词组的意思是:(行动要)像一个大孩子;行为与你的年龄相称。

例子:比尔,不要扔石子,像个大孩子!

虽然汤姆已经是个大孩子了,但总是像小孩一样。