B1 adjective /ˈtʃaɪl.dɪʃ/
Childish
enfantin; immature mais inapproprié pour un adulte
Meaning
immature and silly; behaving in a way that is typical of a child but inappropriate for an adult
Example
His childish behavior during the meeting was quite embarrassing.
Son comportement enfantin pendant la réunion était assez embarrassant.