Plain English Meaning
The angle at which the aircraft cuts in toward the runway centerline when joining a precision approach. A small angle means a gentle join; a large angle means a sharper turn onto the course.
Full Definition
The angle, measured in degrees, between the aircraft's current heading and the inbound course of the localizer, used as the aircraft turns to join the final approach course during an ILS approach.
Context Anchor
Encountered during instrument approaches, especially when air traffic control gives a heading to join the localizer or when the pilot turns onto the final approach course.
Derivation
Intercept' comes from the Latin intercipere, meaning 'to between' or 'catch.' Here, the aircraft is catching the localizer from one side as it flies toward it, and the describes how steeply it is closing in.