A very sick and twisted person.
"Dude, I heard you banged Ms. Phillips last night."
"Yea, it was gross... she had a munch."
'A Munch' was primarily used to describe someone that was cheeky.
'A Munch' has moved on toosay to someone that u want to insult but not actually wanting to say it to their face. It's almost a replacement of something like the bleeps on television.
fuck off, you munch.