When a child who is now an adult and they have a large over bite usually with oblong shaped upper and lower jaw and messed up teeth. Usually is caused from sucking either on titties or bottles or pacifiers for years as an infant through childhood.
When you're having a mmf threesome go to the girl's mouth while she's moaning and move your penisup and down and she'll make a sound similar when you move your finger against a baby's mouth
Dude 1: Dude, my girlfriend hates you now because of the threesome earlier? What the fuck did you do?
Dude 2: i only did the Baby's Mouth on her, whatt ge fuck is she mad about?