0 If you say that someone is grown up, you mean that they are an adult or that they behave in a responsible way:
1 an adult, used especially when talking to children:
2 an adult:
They're a middle-aged couple, with grown-up children.
My children are all grown-up now.
I don't feel very grown-up.
The 12A certificate means that you can't that film unless you have a grown-up with you.
"I'm scared, Dad." "Yes, I know, and sometimes grown-ups get scared and worried too, you know."