Plain English Meaning
A cockpit instrument with a needle that always points toward a chosen ground-based radio transmitter. Whichever way the aircraft turns, the needle keeps pointing at the station, so the pilot knows which direction it is.
Full Definition
An aircraft radio navigation instrument that automatically points to the bearing of a selected non-directional beacon (NDB) or commercial AM broadcast station on the ground. The needle on the ADF indicator shows the relative bearing from the aircraft's nose to the station being received.
Context Anchor
Seen in instrument flying when using older radio navigation, including holding patterns and .