BUFF
This is a covert (somewhat ironic) acronym. Buff actually stands for "Big Ugly Fat Fuck". Be careful when using this acronym. Most big ugly fat fucks already know they're nasty. So if they hear you call them a buff, they may think you're just being sarcastic and using the nomitive sense and definition of buff (i.e. muscular). This word is most effectively used when identifying a big ugly fat fuck who actually thinks he's got a body to be proud of. See also BIF
Bill: (Casually walking down the street chatting with his friend, Ted. Bill spots some fat nasty down the way.)

Bill: "Hey, Ted. Look at that fat nasty dude over there."

Ted: "Yeah, that guy is BUFF"