Plain English Meaning

The pilot repeats the instruction back wrong, the controller doesn't catch the mistake, and the flight ends up doing something different from what was actually cleared.

Full Definition

A communication breakdown in which a pilot reads back an air traffic control clearance or instruction incorrectly, and the controller fails to detect the error and correct it, resulting in the pilot acting on a clearance that differs from what was issued.

Context Anchor

Encountered during radio calls with air traffic control, especially when copying altitude, heading, route, or approach instructions in instrument flight.