Something or someone that one would happily tug his (or her) horn to for sexual pleasure or pain. Normally in preference to pornography or in sadistic cases, snuff films.
1) That picture of your little sister is wankoverable
2) That tablecloth is so wankoverable, I mean it will conveniently catch all my semen and I don't have to clean up afterwards. By the way, thanks for inviting me over for dinner