Literally stands for Designated Ugly Fat Friend. This is the bitch who comes out of no where to cockblock you when you are about to get a chick home with you. She is often recognizable by her fat ass, bad hair and sour disposition. Her main goal of the night is to fend off any advances on her friend so she will have company at the diner when she is stuffing her fat face with an omelet and a side of disco fries while she bitches about anyone and everyone. The D.U.F.F can be defeated with a high level wingman, but you will be expected to return the favor; a job not for the faint of heart. A naked D.U.F.F often smells like a box of crayons.
"Dude, I was about to bag this chick, but then her army of D.U.F.F's came out of no where and pulled her away. She must be a Volleyball player!"
"Did you Fuck the chick at the party?"
"No Fuckhead, I got Duffed!"
A unattractive female who is always seen with another female who is marginally more attractive. It is usually impossible to score with the hotter female without the duff receiving her fair share of the action.
Damn! I so wanna tap that chick.. but goddamn, she always has that duff Nicole hanging off her. Look at that fat mess!