Panfan is an adjective to describe another person, most often a male. Panfan can also be written P.A.N.F.A.N, which simply means Pussy Ass Nigga For Another Nigga.
A male becomes a panfan when he is so overly obsessed with his other male friend that he can even ignore the company of females
Friend 1: "Hey girl how is the new guy?"
Friend 2: "I asked him how his day was and he started telling me about how his homeboys day was."
Friend 1: "Oh, he is such a panfan!"