An individual who identifies as heterosexual, but engages in homosexual activity with a specific individual on an exceptional basis. Very close friends with benefits.
courtney: OMG that girl got big!
sharon: i hear she's turned lesbian.
courtney: ahahaha what a gayfer!
the term gayfer usually carries little-to-no homosexual connotation within it, in the same way that faggot or pussy, many times, have little to do with orientation or genitalia.
person B: "yeah man, what a little gayfer."