(adj): Deriving from drug lingo, "fat bags" describes something that is beyond satisfactory. Something is "fat bags" when it exceeds one's expectations or standards.
Extremelylarge breasts that can not simply be glanced at. Either being so fabulous one can't take their eyes away. Or so grossly saggy one can't stand to look again and attempt to appreciate the attrocity.
(Noun, pl) Tits that are actually just bags of fat; they are totally shapeless, and can only be found on fat people. They frequently cause boner whiplash.
Susan: You have way bigger boobs than I do!
Mindy: No, your boobs are way bigger because they are not even boobs, they are fatbags.