Plain English Meaning
The official set of pre-defined highways in the sky that pilots use to fly from one place to another, especially when flying on instruments. Each route runs between known navigation points and has set altitudes and a fixed width.
Full Definition
The network of published air routes within the United States National Airspace System, established and maintained by the FAA, that connects navigation aids and waypoints to provide structured paths for instrument flight. The system includes low-altitude Victor airways (below 18,000 feet MSL) defined primarily by VOR stations, and high-altitude (18,000 feet MSL and above) used in the . Each has a designated , width, and for and navigation signal reception.