the D.F.F. is the friend attractive girls bring with them, because the D.F.F. is unattractive, so in terms of relativity (see even hot chicks use einstein) the hot chick looks even hotter.
the D.F.F. tends to believe that if they are hanging out with beautiful people they must also be beautiful. what is important here, is that they are wrong.
the D.F.F. is historically the person with who the "wingman" must "take one for the team"
wingman: hellz yeah son
You: I'm gonna go talk to her, oh wait, she has a D.F.F.
1) someone who hangs out with someone else that is much larger then there self
2) someone who is fat and hangs out with skinny people
3) when a skinny girl hangs out with a fat girl to make her look better
yeah holy shit that bitch was huge but her friend was cute
In any group of girls, there usually a couple of hot ones and a token ugly and/or overweight girl, the D.F.F., who supposedly has the best "personality".