Most people would define a fatass, not surprisingly, as someone with a fat ass. But, calling someone a fatass usually has very little to do with the size of their posterior. Pretty much anyone who is considerably overweight is an open target for this word. The problem is that being overweight doesn't necessarily mean you have a fat ass. Being overweight and attending public schools, I was constantly picked on and made fun of as a teenager. The only thing that ever annoyed me was being called a fatass, lardass, etc. The fact is, I don't have an ass. Like many men, my ass is completely flat. I have more back fat than ass fat. I always wanted to jump and show people, but that would only lead to more humiliation. It also really irked me since not having an ass is a real pain if you're fat. Without a big butt to hold your pants up, they fall right off. You either have to wear pants that don't fit, or really tighten that belt to get around the problem of keeping your jeans on. That leads to a pretty bad stomachache by the end of the day. I always wished I really did have a fat ass just to get around this problem. Anyways, next time you're all set to call someone a fatass, make sure they actually have a fat ass.