Plain English Meaning
A radio transmitter on the ground that sends out signals an aircraft can use to find its direction from that point. Each station has its own frequency, and the signals work like spokes on a wheel radiating outward in every direction.
Full Definition
A fixed, ground-based radio transmitter that broadcasts VHF navigation signals on assigned frequencies between 108.0 and 117.95 MHz. The station radiates two signals -- a reference signal and a variable signal -- that allow an aircraft's VOR receiver to determine the aircraft's bearing from the station along any of 360 radials.
Context Anchor
You encounter this term when learning VOR , tuning a VOR frequency, identifying the station, or following a based on that station.