Plain English Meaning
The Morse code beeps each ground navigation station sends out so pilots can check they have tuned the right station and that it is working.
Full Definition
The Morse code identifiers transmitted by ground-based navigation aids (such as VORs, NDBs, and ILS components) that allow a pilot to confirm the station is operating correctly and is the intended facility. Each NAVAID broadcasts a unique two- or three-letter Morse code signal at regular intervals, which the pilot listens to through the aircraft's audio panel after tuning the corresponding frequency.
Context Anchor
Seen in pilot weather reports, route descriptions, , and when a pilot needs to a .