noun. I'm no mathematician. Consult your buttockologist.
Real citation: "Looks good in the front - This is super cute looking...however, rather than a light weight short underneath there are kind of thick panties. The problem with them is that they kind of give you quadri-butt....elastic needs to be a bit looser."
(June 11, 2008, Buzzillions, http://www.buzzillions.com/dz_1263262_skirtsports_marathongirl_ultra_reviews)
Made-up citation: "If you had to choose between pancake ass and quadri-butt, would you forego having a tush altogether?"