1.
( of a person ) to develop into an adult :
She grew up in Boston (= lived there as a child) .
Their children have all grown up and left home now.
—related noun [+ to inf] grown-up
2.
used to tell sb to stop behaving in a silly way :
Why don't you grow up?
It's time you grew up.
3.
to develop gradually :
A closeness grew up between the two girls.