An internet shorthand for "Get Real or Fry."
It is used to bring someone who has lost a grasp on reality and are setting off on an unreal tangent that is not possible to fulfill in their lifetime.
Man 1: Kelly is fairly attractive.
Man 2: She is totally out of your league.
Man 1: I don't think she is. I intend to marry her.
Man 2: GROF, dude.
The sound a Chav makes when hit in the face.
Chav : Yer Mar
You : *smack*
Chav : Grof!