Noun. A contraction of the phrases, 'Frat Boy' and 'Douche Bag.' Meant to save time by combining the two into one. Because frat boys are inevitably douche bags, 'frat boy douche bags' may simply be referred to as 'frat bags.'
John: Dude, I went to that party over at alpha phi douche the other night.
Paul: Oh yeah? How'd that go?
John: It sucked. There were like 2 girls and 45 frat bags.