act one's age

act (one's) age

To behave in accordance with one's expected level of maturity. Really, John, act your age a little. You're like a child sometimes! I'm glad that Sarah is so committed to her studies, but sometimes I wish she would act her age and go out with her friends a bit.
See also: act, age
Farlex Dictionary of Idioms.

act one's age

Behave more maturely. Although the phrase often is used in asking children to act in a more grown-up fashion ( Only babies suck their thumbs; act your age), it also may refer to an adult who is, sometimes deliberately, acting much younger than might be considered appropriate ( Grandpa, it's time you stopped climbing ladders and acted your age).
See also: act, age
The American Heritage® Dictionary of Idioms by Christine Ammer.
See also:
  • act (one's) age
  • act your age
  • Act your age!
  • act/be your age
  • courage of one's convictions, have the
  • have the courage of (one's) convictions
  • have the courage of convictions
  • have the courage of your convictions
  • have/lack the courage of your convictions
  • lack the courage of (one's) convictions