the brown or black crud that's made from a combination of oil, sweat, after-piss, dead dick skin, and, at times, dried up cum, that clings to the crevices of a man's scrotum as a result of not bathing for a month.
Dude: Hey man, your finger nails are dirty.
Man: Sorry dude, I just scratched myself.
Dude: Oh god, is that-
Man: Yup, dick molt.