The highest form of a douche you can get. You have the first stage which is a douchebag, the second stage which is a douchenozzle (slightly more annoying than a douchebag because the nozzle is actually inserted into the vagina), then you have the douchebackwash which is the highest form of a douchebag that you can get/be...because the backwash is the dirty drainage that drips out of the vagina to clean it, thus worse than the bag or nozzle. Used to describe a super super super douchebag.
That guy jus got his car totally tricked out on "Pimp My Ride" then a week later he gets in a wreck an totally demolishes it. He's ok an everything but he's gotta feel like such a douchebackwash for destroyin that slick ass ride"
someone who is the way annoying than your average "joe douchenozzle" and has need for a more insulting insult, because the backwash of the douche is the run off of what actually goes into the skanky, nasty pussy, so therefore calling someone douche backwash is way worse!
Hey, that guy on craigslist with stupid blinder shades flashing 20's and talking trash trying to pickup chicks is nothing more than douche backwash!
Even people all over the net are calling him douche backwash.