Choose the adjective, petulant, to describe a person or behavior that is irritable in a childish way.

The adjective, petulant, is a disapproving term used to describe a bad-tempered child, an adult behaving like an angry child or behavior or this type. Angry or annoyed mean the same thing, but if you choose the word, petulant, you are indicating that it is unreasonable or unjustified. Petulant came to English in the late 16th century from the Latin petulantem "forward, insolent" but was not recorded to mean childishly irritable until the late 1700s.

Definitions of petulant

adj easily irritated or annoyed

cranky, fractious, irritable, nettlesome, peckish, peevish, pettish, scratchy, techy, testy, tetchy
having an irritable and unpleasant disposition