It means the same thing as immature, just this way of saying/spelling it is so much better. Hey, it makes sense doesn't it? Yes. It definitely does.
Stop being so unmature.
by Ashley Aguiar December 10, 2004
by Not mature January 28, 2019
Unmature: Consistently insulting someone daily for no good reason. And getting mad at someone for nothing.
I made this up
I made this up
by Tommish August 01, 2021