A person (gender doesn't matter) who constantly acts like they own the entire country and that they're famous/beloved by all, when in truth they're morons/assholes that nobody likes.
I hear you're new to the neighborhood. First of all, please ignore Joe. He's one of those "small man, big ego" types who thinks he owns the street. I should know, I'm his landlord.
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi