Someone who thinks that carrying a gun, knife, cosh, potato peeler, etc makes them in some way a force to be reckoned with 'on da streetz'. Preferred methods of 'combat' if they ever get that far are anything that avoids harm as much as possible, such as drive-by-shooting or spraying fire randomly into a crowd.
Or, in simple terms, a cunt.
Chav: Gimme some respect, I's a soulja, innit!
Non-chav: No, you're a cunt.