A term used to describe girls, usually big breasted women who are wearing a bra that is too small for them so it looks like they have four boobs.
I bought a bra the other day and thought it would be good to wear to the club, but i started dancing and noticed I had quadraboob. My nipples were hangin out.
It's when women wear bras that are too small for them which causes the boobs to fall out of top of the cups. This leads to the impressionthat there are 4 boobs under their shirt instead of 2.