Designated Ugly Fat Friend.
typically seen at a bar or night club with any attractive female. They are put on this earth for one reason, to cock block. They usualy give you dirty looks while you talk to there friend then tell you that shes to drunk and makes the girl leave.
YOU WILL ALWAYS SEE A DUFF WITH ANY GOOD LOOKIN CHICK!
"Dude i was so gonna fuck that chick tonight but her fat fuckin duff mad her leave."