A person who acts stupid but is really smart but only when it is needed.
Lets say Bob goes to school and steals some cafeteria food, pretty stupid. But when he takes his Algebra final he makes a 100. This would be a jawmuncher.
This word is commonly used in middle and high school when talking about a friend that does stupid things outside of school but is smart inside of school.
a person who is not jewish, but hangs out and surrounds themselves with jews so they might as well be. and they also probably munch on jew dick/puss , hence the muncher part.
Bro 1: yo dude you know that kid ben isnt even jewish?
Bro 2: hes a fuckin jew muncher , he might as well be.
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi