This phenomenon results from pounding an anus not fully cleaned of feces.
The term is often used when speaking of homosexual sex.
A muddy helmet is sometimes referred to as a "fag fuck cock collar" or a "shit kiss".
Last time you pounded that faggot Andre's ass, you had to use pineapple juice to get the mud off your helmet. What does that little hissy fit queer eat anyway? Motor oil?