"Route 50" is the act of Anal Sex. It's is not defined by the gender giving or receiving the said Anal Sex.
"Route 50" originated when this definition's maker banged his girlfriend in the ass, on the hood of the car, on the side of Route 50, at 2 o' clock in the morning. Any venturing into the anal cavity with either a penis, or an object designed to replace a penis is to be known as "Route 50."
Mike: "I route 50'd your mom last night!"
James: "Hey, as long as you don't get her pregnant, I won't complain."