A word said when one starts to say douche bag but decides mid-word that it would be innapropriate for his surroundings so he tries to say d-bag instead. It can also be used when someone feels the word douche is too harsh, yet has already started to say it.
Forrest sits at lunch as a teacher walks past the other side of the table. "Lauren, stop calling Tim a walking joke, you're such a doo-bag" (forrest tries to stop "douche" midword and replace it with "d", but is too far through "douche" and doo-bag comes out)
A small, dirty piece of male white trash, usually with an under-developed peachfuzz moustache, greasy longish hair (preferably a mullet), and a faded heavy-metal concert t-shirt. Usually the guy you go to last to buy a sack.
I don't go to monster truck rallies. Too many doobags.