(noun) A somewhat foolhardy, often poorly dressed white person. It is almost always used by any other race besides caucasian, to describe a caucasian acting foolish, saying something dumb, and in general being stupid.
The guy who was Gengis Khan's best friend and lover (for more information, check The Secret History of the Mongols), but Jamooka pulled some shit pissed him off and Genghis killed him. To be used whenever someone does something fucked up to a friend.