The juveniledefinition is simnply of a snitch but a rat is really a traitor. If you're onvolved in crime or a gang & you snitch, you are a rat -- & rats must die!
Me & Jimmy whacked that gas station dude cuz he was slow with the money we wanted, then, when the pigs questioned him, he was a wuss and rolled over on me -- so I got to whack the little rat now!