Baby's mouth

When you're having a mmf threesome go to the girl's mouth while she's moaning and move your penis up 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?