Meaning of “childish” - Learner’s Dictionary

childish

adjective uk us /ˈtʃaɪldɪʃ/
SILLY

B2 Childish behaviour is silly, like that of a small child:

Don't be so childish!
OF CHILD

B2 typical of a child:

childish handwriting
childishly adverb
childishness noun [ U ]

(Definition of “childish” from the Cambridge Learner’s Dictionary © Cambridge University Press)