Josh: hey, you want to hang out?
Corey: nah i can't, i'm chillin with my girl today.
Josh: damn dude your a babyass...

kaitlyn: yo ash hows my ass look in this bathingsuit?
ash: ahhh, you have a bad case of baby ass!

Person 1: Do you see that man over there? He’s a baby ass.
Person 2: Yeah, 22 year olds are so immature.

You basically use it to make fun of someone.