Either of two persons who instance on farting in front of each other.
One of two persons who join up together to fart in inappropriate settings.
Either of two person who share an intimate relationship and think it's funny beyond belief to out do each other by farting incessantly.
Mary and John are not only married but fartners in crime. Have you ever stayed at their home?
Don't go to dinner with Bob and Gerry. They are fartners true and true and public displays are their MO.