Plain English Meaning
One published route in the sky that two different kinds of aircraft can use: older ones that follow ground radio stations, and newer ones that follow GPS-style waypoints. Same path, two ways of flying it.
Full Definition
A high-altitude airway that serves both as a conventional jet route, defined by VOR navigation aids, and as an RNAV (area navigation) route, defined by waypoints. Aircraft equipped for VOR navigation can fly the route using the ground-based stations, while RNAV-equipped aircraft can fly the same route using their onboard navigation system and the published waypoints.
Context Anchor
Seen on when a Jet route and an are drawn together along the same .