1. An unfathomable moron
The word JackMonkey was origonally a derivative of "jack off" that was created in a moment of absolute frustration. The defining factor of a JackMonkey is their inability to grasp even the simplest concepts that are new to them.
I tried to teach that JackMonkey to tie his shoes but all he managed to do was get his fingers stuck in knots.
The person in your life who will not leave you alone and/or wants to be like you. One who clings like a monkey and is always on your jock. This includes but is not limited to the following behavior: dressing like you, acting like you, using your patented clever phrases (like "jockmonkey"), remembering past events in a way that makes it seem you are actually copying off of them.
My jockmonkey got an eagle tattoo on his forearm a year after I got a swallow tattoo on mine.