Plain English Meaning

When a spinning instrument inside the panel gets pushed too far and loses its bearings, so the needle swings wildly and stops showing useful information.

Full Definition

An erratic, uncontrolled spinning of a gyroscope's rotor or gimbals that occurs when the gyro is forced past its mechanical limits, causing the instrument to give false or unusable indications until it is reset or re-erected.

Context Anchor

Seen in discussions of gyroscopic instruments, including the turn-and-slip indicator and other instruments that use a spinning gyro to sense aircraft movement.

Derivation

From the everyday sense of 'tumble' meaning to fall or roll over uncontrollably. The word captures what happens inside the instrument: the gyro stops spinning smoothly on its axis and rolls around on its mounts.