When a couple is engaged inintercourse, then one of the two proceeds to excrete fecal matter onto the others face, and then shaves his(or her) pubic, taint and ass hairs on top of the crap, as to imitate Matt Damon's beard. (distant relative of the abe lincoln)
Oh my Gosh hun, that dirty damon was so thorough that if I saw you on the street with all that crap and pubes on your face, I would have asked you for your autograph!
a Dirty Damon is when one shits in another mouth and the person with the shit in the mouth try's to gargle it then spread it on the others face while putting their pubes and ass hair on the others face making it seem like they are a dirty Damon they then proceed to suck the other off and then spit the cum on the others face adding to the mix of shit and hair.