What most adults act like...
WW1,and 2, all wars, Holocaust, 9-11, slavery...etc
To act with qualities of a child. Most often considered negative, however, children also have positive qualities. Therefor, Childish can be positive... such as cute, whimsical, and playful. It can also be neutral. Somebody who curls up at night with a stuffed animal is childish, but this is not the least bit negative.
Awww... my GF is so cute and childish, I'm gonna go get her some Hello Kitty stuff.
What many adults prentend not to be, and what many childen aren't.
Bob "I'm so childish"
Steve "Nothing wrong with bein' childish now and then. We all are at some point."
A word students at Evans Middle School uses ENTIRELY too much!
"Bruh you childish"
I hate childish people, especially if they are authority figures.