A term of endearment, used by a man or a woman, in reference to their partner, after the man ejaculates either inside of or over the other's anus. Also, can be used as a derogatory term for gay men, but only rarely, and in jest amongst straight men, who are feigning 'gayness' for the amusement of friends and/or family.
Gay guy #1: 'Hey there, slippery-tail, how'd you like that last bung-load?'
Gay guy #2: 'Ohhhhh, marvelous, my jizzy-boy, thanks kindly, when may I have another?'
Gay guy #1: 'Hold your horses there, humpy-buns, I gotta reload and do some more coke.