Shorthand for Gay-Nigga-Itis. Symptoms: Flu like symptoms, Back hurts, Pussy hurts, Complaining about shit you cant control, excessive thoughts of dick.
Person 1: man, I've really been dealing with some horrible back problems lately.
Person 2: Damn, sounds like you got a case of GNI
Person 1: GNI?
Person 2: Gay-Nigga-Itis