origin: German; munter= cheerful, jolly, blithely.
1. British slang; an unattractive person (most often used against women), although this particular insult implies a person whose specifically a mess due to an overuse of drugs and/or alcohol. Ex: A person whose make-up is sliding off their face, hair matted with sweat, heels covered in mud, as they puke against a tree.
I mean, if you're an immature party person, you don't want to see a giant visual reminder of what you may look like to another (or may become).
2. Munter (hitch) is a type of knot used by mountain climbers. In German, the fantastic word for it is: Halbmastwurfsicherung.