Plain English Meaning
A knob or lever on some gyro instruments that lets the pilot freeze the gyro in place so it doesn't tumble or drift during unusual maneuvers, or to reset it to a clean starting position.
Full Definition
A mechanism on certain gyroscopic instruments, such as the attitude indicator or directional gyro, that allows the pilot to lock the gyro's gimbals in a fixed, centered position. Caging stabilizes the instrument during maneuvers that would otherwise exceed its operating limits, or resets it to a known reference before flight.
Context Anchor
Seen during the before-takeoff , especially when confirming that the attitude indicator is ready for an .