Someone that is grown on the surface, but is a child and a clown beneath the surface facade.
The reverse man child/girl child looked and sounded serious, but really he/she took nothing seriousy and held nothing sacred.
Man child boi is similar to the common phrase man child but is more insulting to the person receiving it because of the "boi" at the end
Stop being a man child boi and get out of the dishwasher
1: have you seen Caden?
2: yeah he is such a man child
Carlos Duran of Lincoln Park MI
Grown man that acts like he’s 18
Person 1 (over age 34): bro let’s go get fucked up and shots tonight, I bet I can out drink you!
Person 2: your such Carlos Duran Man child.