immature
adjectiveUK /ˌɪməˈtjʊə/
US /ˌɪməˈtʊr/
Not grown up yet or acting like a little kid.
The immature puppy chewed up my shoes.
RELATED WORDS
OTHER MEANINGS
2. Not yet fully developed or ripe, as with fruit.
The immature apples were too sour to eat.
3. Behaving in a silly way that is not right for one's age.
It was immature of him to laugh at the mistake.
4. Not yet fully formed or complete, as with a plan or idea.
Her idea was still immature and needed more work.