Another name for a homosexual man. Sometimes referred to as a rainbow fish. There are many fish in the sea metaphorically, but mudfish tend to seek out mates of the same sex. They get this title because of the mud-like fecal matter that coats their genitalia after sexual intercourse.
A variation on the popular shocker, the mudfish incorporates the use of the pointer finger, with the middle finger bent and the pinky and ring fingers stuck straight out. The pointer is inserted into the vagina, while the ring and pinky fingers are inserted into the anus. This name speaks to ones desire to venture into dark muddy places, just as certain fish do.
After I gave her the mudfish, she didn't poo right for a week.