1. A happy affirmation in an imaginary fox language, invented by the writer of the Fuzzball MUCK server. The definition was confused with the definition for another word in the same imaginary language, 'yipp', and an administrator of another MUCK heavily promoted 'yiff' word in its first known sexual connotation in 1995 or later. It was only after this point that supposed origins concerning mating sounds and acronyms were invented.
2. Meant to imply feelings of sexual arousal or intent to arouse; also refers to a sexual act. Considered crass language in polite circles.
1. "Yiff!" (Happy affirmation in imaginary foxish language.)
2. "Yiff!" (I am feeling aroused.)