Basically a douche bag but just being extra duffely. It means nothing so if you were wondering, why you see this on facebook, don't worry it just means douchebag but it sounds a little cooler. Also, if you're too much of a coward to call someone a douche (bag) to their face, you can just mutter under your breath a shortened version, "duffel bag.."
*Obnoxious guy throws a girl's paper from her desk onto the floor.*
Girl: your'e such a douche duffel bag
Guy: ...you did not just call me that.
Girl: u mad?
*Big bull pushes scrawny little freshman into a locker.*
kid: duffel bag
bully? WTF does that even mean?! stupid little freshman *walks away*