(Noun) An idiot from New Jersey. Most notably encountered while driving. Known for cutting people off, riding up your ass, bald tires in the snow, and just plain old being stupid while attempting to operate a motor vehicle obviously direction indicators (turnsignals) are an option on the vehicles they drive. Just one look at the plates on the vehicle explains it all; its a njidiot.
Hey Joe, That persons a njidiot.
How do you know that Bob?
He has Jersey plates and by the way he is switching lanes it seems that he didn't purchase the optional directional signal package.