act one's age

abound in one's own sense

To follow one’s own inclinations and opinions.

ace up one's sleeve

A surprise advantage of which others are not aware.

act of Congress

An authorization that is extremely difficult to obtain, especially in a timely fashion.

act one's age, not one's shoe size

Synonym of act one's age (“to behave in a mature manner; to avoid being childish”).

act out

To perform something specific.

act the hypocrite

To behave deceitfully or hypocritically; to dissemble.

act up

To misbehave; to cause trouble.

afraid of one's own shadow

Exceptionally timid.