A term of utmost hatred used to define someone with a weight problem; this term should not be used in reference to someone who could kick your ass, only in situations where the fatass is totally immobile or just a pussy.
Hateful Person: Put those Cheetos down you fucking fatback Fatback: Dude, I'd hit you if I could get up off this bed.
Hateful Person: Yeah, you're fuckin-a right you grotesque fatback mother-fucker.
By Amandy
Fatback
A layer of buttery cheese commonly found on a sorostitute's back, just above her waist that usually shows signs of dunlap disease and may or may not be accompanied by a large stripper tattoo. This type of fatback is mostly caused from drinking beer and eating large pizzas all by themselves. Possibly a major portion of their freshman fifteen.
I went home with Samantha last night -- I didn't have a condom but the fatbacking was great.
By Lynna
Fatback
The extra amount of skin (fat) that droops over the back and sometimes sides of girls bras. Usually happens when they are too fat or the bra is too small.
A referal of a females backside or booty, appealing to the opposite sex, which is man. (No Males should have a fatback. Females are stricklyforbidden to use this world unless your gay).
A girl who is rather heavy, yet not totally obese, in a fairly sexy way. It is a common term of endearment for the larger girls, who are not fat, but sexy.