A Best-Friend-Forever-Girl- Friend.
A very rare instance in which a girl of a man's dreams that he is seriously dating is also his best friend. Sharing similar interests, outlooks on life, beliefs and genuinely enjoying one another's company are essential qualities in determining whether a girlfriend can be moved into BFFGF territory.
Guy 1: Do you see that look in Lance's eyes whenever he is talking to Samantha?
Guy 2: Yea man, she is totally his BFFGF
