A monkey's hard cock. Used for insults and lack of come backs.
Came into use when a girl got tired of your mom and your face insults.
bob: you are a motley fool.
girl: You suck monkeybone.
boy 1: Say what? That don't make no sense.
boy 2: You're so hard-headed.
random boy: Yeah, you're such a monkeybone.
An extremely stupid (but good) movie about a cartoonist, his most famous creation, his girlfriend, and the dream world. Don't watch it if you hated Freddy Got Fingered or if you are adverse to talking monkeys.
I still remember when I rented Monkeybone...Shawn B. and I laughed so hard, we almost choked to death...