I . ˌgrown-ˈup
adjective
1.
( of a person ) mentally and physically an adult
SYN adult :
What do you want to be when you're grown-up?
She has a grown-up son.
2.
suitable for or typical of an adult :
The child was clearly puzzled at being addressed in such a grown-up way.
II . ˈgrown-up
noun
(used especially by and to children) an adult person
SYN adult :
If you're good you can eat with the grown-ups.