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. © 2015 Farlex, Inc, all rights reserved.

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. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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