a person that is super douchey, like double the douchiness of a normal douchebag, hence the contraction of deuce and douche. The pronunciation of deuche is similar to douche, so no distinction can be made when merely heard. One might specify that they are calling someone a "eu" deche rather than an "ou" douche, but in doing so, this makes that person even more douchier as well. It just spirals into one douchier circle with no escape. In fact I should stop typing now.
"See that guy with the Affliction shirt, what a douche, oh he even has an affliction hat......DEUCHE"