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.
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 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.
A referal of a females backside or booty, appealing to the opposite sex, which is man. (No Males should have a fatback. Females are strickly forbidden to use this world unless your gay).