noun: the slow pressing of human feces between one's fingers while performing the act of fisting one's anus
After a long night of heavy drinking (or not) as you fist a girl in the anus, your hand cramps open to the point where a smooth extraction is impossible forcing the girl to attempt to push your hand out as if she were pooping. During this painful attempt to free your hand, you begin to feel a sensation between your fingers similar to that of hot smooshed-up bananas, being, of course the seepage of her feces.
"Last night I was up in this girl's shit, literally man. I got it stuck up in some mad seepage."
When your dick starts to stick out through the hole in your boxers. Generally happens when you wear loose-fitting boxers with plenty of move-room or have an erection.
Duuuude, I had some major seepage this morning and when my mom came to wake me up, she saw my dick in its full throbbing glory!
When a woman not using birth control uses an anal tampon, or really any tampon of the right size, and inserts it into her anus post anal sex to soak semen and prevent sperm from leaking into her vagina and causing an anal fart baby. Some of the semen is absorbed into her intestines, some of the semen is shat out before and after the insertion.