That one person who has the uncanny ability to partake in douchery but does not exibit all the qualities of a typical douche, leading some people into the illusion that this person is not in fact a douche. In many cases a closet douche is only a douche to guys so oblivious girls think hes a cool guy, adding to the hatred of him. Also, creatine is used by certain closet douches to artificially bulk them up, but everyone knows it just shrinks their ballsack.
guy: "God damn Bob is such a douche"
oblivious girl: "No he's not, he's really a nice guy and he's so muscular."
guy: "No he definatly is, it's just he's just a huge closet douche."