Plain English Meaning
A radio in the aircraft that listens to navigation signals and tells the pilot where they are or which way to fly to get somewhere.
Full Definition
An airborne radio receiver that picks up signals from ground-based or satellite navigation aids and converts them into usable position, course, or guidance information for the pilot. Examples include VOR, ILS, ADF, DME, and GPS receivers.
Context Anchor
Seen in discussions of navigation and communication equipment, especially when describing the radios and displays used for instrument flying.