A term used by auto mechanics to describe oil leaks that aren't that bad, but will be soon.
"Hey Xavier, is that oil pan bad?"
"Naw man, it's just got some seepage"
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."
Jism leaking out of a birds snatch after shagging that dampens her gusset and sometimes dampens her Jeans too. Maybe even the chair she's sitting on.
Clean yourself up bitch! If you're going to shag in the toilet at least you can bung it and prevent seepage!