Combines Merge with Sociopath. Defines a driver (usually male, usually talking on a Bluetooth device, usually driving a luxury sports sedan), who passes up an entire line of vehicles at an offramp before cutting/forcing their way into the line at the last possible moment before the exit.
Mergeopath's are self-absorbed, obviously far too important to wait in line like the rest of the common commuters, and cause an immediate rise in the blood pressure level of all those who are aware of their assholish conduct.
(wife on cell phone talking to her husband)
"Yeah, honey, I should be home in about twenty min...OH CRAP (sound of brakes and a purse flying off the passenger's seat to the floor)! I JUST GOT CUT OFF BY SOME DAMNED MERGEOPATH!"