/ ˈtʃaɪldɪʃ; NAmE / adjective
1.
connected with or typical of a child :
childish handwriting
2.
( disapproving ) ( of an adult ) behaving in a stupid or silly way
SYN immature :
Don't be so childish!
OPP mature
—compare childlike
► child·ish·ly adverb :
to behave childishly
► child·ish·ness noun [ U ]