childish

/ˈtʃaɪldɪʃ/

adjective

Meaning

Of or suitable for a child.
Behaving immaturely.
"Your childish temper tantrums are not going to change my decision on this matter."

Synonyms

immature,

infantile,

juvenile,

puerile,

silly,

unbecoming,

childly,

juvenile,

kiddish