B1 adjective /ˈtʃaɪl.dɪʃ/
Childish
kindisch; kindliches Verhalten, aber für einen Erwachsenen unangemessen
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.
Sein kindisches Verhalten während des Treffens war ziemlich peinlich.