the true "definition" of mudbutt,(all the rest are other peoples versions) is: the condition of the anal region where ones crevice between the ass cheeks becomes hot and saucy due to sweat, buildup of underwear residue, and poor wiping abilities. It is almost certain to happen to anyone on a real hot summer day if they:
1)wear dirty and/or heavy clothes
2)do not shower
3)have recently deficated
4)have participated in exercise
After walking through the city all day with a pair of jeans on, John developed a case of "mud-butt".