That place on the human body (particularly the female body) where the body makes contact when sitting-down, i.e. the erogenous area of the butt.
The shake at the bottom of a bag of drugs, including the seeds and stems in a bag of weed. Commonly used to describe the shake at the bottom of a bag of crystal meth.
Jeff: Hey, let me get a ball of that fire ice. Dan: All I have left is the duff, bro.
Duff the DESIGNATED UGLY FAT FRIEND as a duff i would know its not fun ,sometimes u get ignored by ur friends and you feel left out
"I was a DUFF back in middle school."
That fat bitch over there, with those other girls, is so ugly... she is such a duff.
Designated Ugly Fat Friend
Every group of friends has one. The duff is someone who makes the rest of the group look better. The duff hides the rest of the group's flaws.
However the duff doesn't technically have to be ugly or fat, they could just be not as good looking, or maybe they are more approachable.
To know if your the duff just think have any guys/girls asked things about you or have they only spoken about your friends?
An even easier way to find out is to look around your group of friends and if you can't spot the duff then it's probably you!
Then again EVERYBODY is someone else's duff, so there's no need to worry. You are a duff.
Deal with it!
Be proud!
Take advantage of it!
"Damn! Those girls are hot, but maybe we should speak to their duff before approaching them!"