A doochebag can be any one of 2 things.
1. A bag used for squirting water up your ass, In some vain attempt to "clean" (HA) your bummhole out.
2. It is also possible for one to be a doochebag,
ie, if you do almost anything homo or vaguely irritating in any way, you could be a doochebag
Hmm... i need to clean my ring out... Ill go get a doochebag
You fuckin doochebag