Quad Chin
When a person, usually overweight, has large amount of fat under there chin resembling extra chins. A quad chin is two double chins combined.
Her: Holy crap, that fatass has a double chin!
Me: No, all that layer of chin is a quad chin
Me: No, all that layer of chin is a quad chin
Quad Chin
When yo balls hit the girls chin when she sucking your penis
Hey Stacy guess who got an quad chin last night!?