A douche bragger is someone who often feels the need to brag to others about the overexaggerated stupid shit they have done. Basically informing us on how much of a douchebag they really are.
"I LOVED opening that check for $4000 after doing that acting gig" annouces Cam(Douche bragger in question)
"shut the hell up! and get your own bed.... ya douchebragger," says the homeless bloke sleeping on a park bench.