Plain English Meaning
An approach where the pilot has lost their heading instrument, so the controller watches them on radar and tells them when to start and stop turning instead of giving compass headings.
Full Definition
A radar approach used when the aircraft's directional gyro or other heading-stabilizing reference has failed. The controller observes the aircraft on radar and issues turn instructions as 'turn left' or 'turn right,' which the pilot begins immediately and holds until told 'stop turn.' Once on final approach, turns are typically reduced to half standard rate.