A combination of the words "douchebag" and "fucktard" (a fucking retard). It is a very big insult and should not be taken lightly.
David: No, I don't know and I'm not going.
Ashley: YOU'RE A DOUCHEFUCK, DAVID! A BIG FAT MAINSTREAM-ADDICTED DOUCHFUCK!
David: Whatever. What does Mainstream mean?
Ashley: I am disappoint, son. I am disappoint.