Childish
Childish (chīld"ish) , adjective
1.
Of, pertaining to, befitting, or resembling, a child.
Childish innocence.
2.
Puerile; trifling; weak.
Methinks that simplicity in her countenance is rather childish than innocent.
Childish, as applied to persons who are grown up, is in a disparaging sense; as, a childish temper.