means "Grenade Free America" used by the cast - mostly Mike and Pauly D - of Jersey Shore. used in season 2 of show when in miami and describing that they will not hook up with any grenades - ugly women - during there time there
Pauly D - "Me and Situation have a gameplan for there to be no grenades in Miami. 100% No Grenades!"
Mike - "It's a GFA, Grenade Free America."