Two hot chicks at a bar will have a really nasty fat ugly bitch hanging out with them, refered to as a "DUFF".

"Wow that fat DUFF is hanging out with those two attractive ladies, too bad."
by Cobra January 27, 2003
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That 3rd girl is definitely the duff of the group.
by G January 2, 2004
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A real term used in the heydays of Cocaine frenzy, 70s, 80s. Duff refers to that portion of your cocaine that consists of powder only, usually full of cut or anything else but real cocaine.
Shit, I won't buy from that dude again, this is all duff.
by Gojai August 30, 2017
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A simple pudding eaten by 19th century sailors. This was given to the crew once or twice a week at the most if they were working hard, or if the captain wanted to motivate them. Consisted of flour, boiled water, and whatever available fruit or molasses. Considered to be quite a luxury.
Having been unruly, the crew did not receive duff last Sunday.
by electronic_rodent April 13, 2008
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Designated Ugly Fat Friend. A book written by Kody Keplinger. Also a movie. Basically it's the person in a group of friends that is less popular than the rest, isn't as pretty/handsome, or they are a bit thicker than the rest. Sometimes it can be a freshman with a group of juniors or seniors. The Duff can be someone other people go to to get information on the Duff's hotter friends.
Emily = The Duff
Hot guy : Yo Emily!

Emily : *omg a hot guy is actually talking to me!!*
Hot guy : hey, do you know if your friend Hannah has a date to homecoming? I want to ask her to go with me.
by NWinchester January 12, 2016
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duffness- A name you can call someone or something without offending them up front. Clumsy, silly, jerk, funny, asshole, comedian, joker, dork, jerkoff, lame, pussy, fatass, drunk, idiot, rapper, skelator, bandit, clown, jester, tattoo, pig, fool, cholo, ganster, thug.
Kid tells his mom: Look at that clown his a duffness!
A boyfriend tells his girlfriend: Your a duffness for acting like that.
Audience: Look at the rapper acting like a duffness after the show.
The man was at the resturant eating a burger like a duffness
The duffness got cought robbing a bank
by T.F. King #1 May 11, 2011
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Designated,ugly,fat friend.

You don't necessarily have to be fat,or ugly to be one. the duff is considered a duff when he/shes significantly less attractive out of the group of friends they hang out with and both boys and girls can be one.
They are often used to get information about his/her friends.
1# "Damn, those girls are hot...well except for that one"
2#"yeah..maybe we can get some info on them from her?"
also shown in the movie"The Duff" if you need a visual example.
by Guade April 2, 2015
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