1. During cunnilingus, the appearance that the pubic hair of the recipient is actually the facial hair of the performer.
2. A euphamism for oral sex
"Dude, I was going down so hard on that chick, I had a total munchstache!"
An edible form of facial hair usually located on the upper lip below the nose.
Henry: Is that a piece of chocolate on Frank's upper lip?
Peter: That's no piece of chocolate, that's a munchstache.