Plain English Meaning
A receiver in the aircraft that picks up the signal from a chosen ground radio beacon and swings a needle on the cockpit display to point at it. Whichever way the needle points, that's the direction of the station from the aircraft.
Full Definition
An aircraft radio navigation receiver that automatically points to the bearing of a selected ground-based non-directional beacon (NDB). The cockpit indicator needle rotates to show the direction from the aircraft to the tuned station, allowing the pilot to track to or from that station.
Context Anchor
Seen in older radio navigation, instrument panels, navigation checks, and that use a non-directional beacon.