Plain English Meaning
Imaginary lines that spread out from a VOR station like spokes from a wheel hub, one for every degree of the compass. Each line is named by its compass direction from the station, so the line going due east from the station is the 090 radial.
Full Definition
Magnetic bearings extending outward from a VOR (Very High Frequency Omnidirectional Range) ground station. A VOR transmits 360 radials, one for each degree of the compass, allowing a pilot to identify their bearing from the station and to track inbound or outbound along a chosen radial.
Context Anchor
Seen on IFR enroute charts, , and VOR displays, especially when identifying , , and near a VOR station.