Someone who intentionally targets and expels douchebaggery to his/her victims. Unlike a douchebag, though sometimes confused, that unintentionally expels douchebaggery to victims. Being a douchecanoe is the apex of douchebaggery going from prick, dick, asshole, douche, douchebag, and finally douchecanoe in progressive order.
It's like everyone is living in an ocean and people all float. Douchebags are floating too but unintentionally hit people and release their douchebaggery, meanwhile douchecanoes target people that they've want to fuck with.
Dylan: Dude I have a story to tell, so my roommate.. or ex roommate... banged my girl in my bed when I went to go take a shower and then left the semen on my pillow so when I layed down that night I almost put my head on it.
Wolfy: l feel for you man, that guy's a douchecanoe!