Plain English Meaning

Inside each ear are three small loop-shaped tubes filled with fluid, one for each direction your head can turn. When you start or stop turning, the fluid sloshes against tiny sensors, and that is how your brain knows you are rotating. Once a turn becomes steady, the fluid settles and the sensation of turning fades, even though you are still turning.

Full Definition

The physiological process by which the three fluid-filled semicircular canals of the inner ear sense rotation of the head about its three axes. Each canal lies in a different plane (roll, pitch, and yaw). When the head turns, the fluid inside the corresponding canal lags behind due to inertia, bending tiny hair cells that send rotation signals to the brain. These canals respond only to angular acceleration (a change in rotational ), not to steady, sustained rotation.