Deriving from the words "would you do her" this word is usually said among males when two or more spot a female person that there is a question of whether or not she is fuckable. It is meant to be said loud enough where only the male participants can hear. The "Jadooer" game is often played out of boredom.
"Hey Matt, Jadooer?"
"Oh, most definitely, I would knock the bottom out of that, and make her swallow the cum."