childish

The boy is unusually self-reliant and mature but also childish and understandably vulnerable.

Since female swimmers, like their male counterparts, tend to be tall, the video only served to make Gaines look childish and came at the expense of her athletic image.

Why would he even engage and respond to this childish stunt?

I mistakenly thought we might still be playing a childish language game.

Guests lit up with childish excitement and impatience.