Someone who thinks that they are the shit. And to some extent, they are. A true prima douche will not do this without reason, however. They will have the talent, and at least as much ego
Their success has gone to their head, and if they weren't their own biggest promoter before, they are now. See most bands' frontmen, and Kanye West.
Becoming a meme could be the best thing to ever happen to Kanye's career. All because he is a prima douche.