Plain English Meaning

When a runway has standing water on it and the airplane is moving fast enough, the tires can skim across the water instead of touching the pavement. When that happens, brakes barely work and steering becomes very limited.

Full Definition

A condition that occurs during landing or takeoff on a wet runway when standing water is unable to escape from beneath a fast-moving tire, causing the tire to lift off the runway surface and ride on a thin film of water. While hydroplaning, the tire loses contact with the pavement, dramatically reducing braking effectiveness and directional control. The minimum at which dynamic hydroplaning can begin is roughly nine times the of the (in ) for a non- tire.