V. To plan a sexual encounter and back out soon after, to stand up.
He said he wanted to be with me, but then he duffed out and changed his mind.
by Laurie-Bell February 01, 2009
short for: Damn ugly fat friend

almost every group of girls has one, but if you can get in with the Duff you can get in with the group cause the girls trust the Duff
Guy 1: Damn, Lindsey is the duff in the duff in that group. She's so gross.

Guy 2: Yea but if your cool with her, she'll put in a good word with Jessica for ya.
by homeboy16 July 10, 2008
"designated ugly friend"

an ugly poor girl you use to laugh at. She has such a scummy pathetic life and drives a 2 dollar pos. Her face is ugly too. Her family is fucked in the head and she makes you feel better about yourself. Though you don't have to, she can make anyone feel better about herself since her life is such a piece of shit.
Boyfriend: don't call the duff tonight, she's too psycho to hang out with.

Girl: Don't worry, i won't, i don't hang with her anymore, it ruins me reputation.
by tawns02 November 16, 2008
Designated Ugly Fat Fuck. A girl that your hot friends bring so you can't get any good pussy.
"Dude, were you able to bang Amy last night?"
"No! I was so mad; she brought her DUFF Caroline!"
"That sucks..."
by Bo C. May 06, 2007
a duff is another definition of a noob; a term used when sombody makes a stupid mistake or does something stupid.
Alex: oh my god my ball hairs itch like hell, man.
Morgan: wait, you have hair on your balls.
Alex: wow, your a fucking duff.
by DJCVans June 30, 2006
to spill something on your clothes.
I duffed my coffee this morning during the commute.
by Argh Dammit September 12, 2005
useless or not worth keeping
that bloody acoustic pinger is duff again
by Barry Grace March 16, 2003

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