[ no passive ]
1.
to gradually develop into a particular type of person over a period of time
2.
( of a child ) to grow big enough to fit into a piece of clothing that used to be too big :
The dress is too long for her now but she'll grow into it.
3.
to become more confident in a new job, etc. and learn to do it better :
She's still growing into her new role as a mother.