noun. An accomplice in horizontal-mambo-type activities.
Real citation: "The Scene - Notice that it is just Jesus and the woman. All the distractions of her life have been removed. None of her 5 ex-husbands are present. Her current co-fornicator is nowhere around. None of the women who so intensely hated her and her lifestyle are to be found here. It is just her and Jesus."
(Alan Carr, The Sermon Notebook, 2003, http://www.sermonnotebook.org/new%20testament/John%204_1-30.htm)
Made-up citation: "She calls me her partner; I call her my co-fornicator. Probably not a good sign."