A person who is real nasty. So nasty they do anything to anyone. Often sexual in nature. You don't wanna mess wiv these badboys. still they are not to be confused wiv the nastyboys of www.nastyboys.com who are actually rather gay and pornographic.
Chris: Why did you hit that man on the head wiv your sledge hammer and then piss all over his face?
David: Beacuse im a NASTYBOY!!
when you're holding up your phone and making faces at it, as though you are taking a selfie, but you're really taking a picture of the person across from you or the wall or anything else that seems interesting but you don't want to be caught dead taking a picture of.
This action is often made more convincing by wiggling the eyebrows or opening the mouth, to pretend you're trying to get a Snapchat filter to work.