The sexual act of masturbating into your open hand which, when covered in spunk/juice, clench and use to fist your mother's brother (or anyone who likes it).
I didn't know my Uncle was such a devianttill he asked me to munclepunch him.
comes from the word 'monkey skull'
where the head grows out at the back so you look like a deformed fucker. !!munckles may cause bullying!!other forms of the munckle are the garfunckle, trifunkle, quadruncle, ect.
shayne has the biggest fuckin munckle on the back of his head. no wonder no one likes him.