Plain English Meaning

When the runway is wet, the tires can ride up on top of the water like a water ski instead of gripping the pavement. When that happens, brakes and steering through the wheels do almost nothing.

Full Definition

A condition in which a tire rolling on a wet runway loses contact with the surface because a layer of water builds up between the tire and the pavement, dramatically reducing braking effectiveness and directional control. Three forms are recognized: dynamic hydroplaning (water pressure lifts the tire off the surface at speed), viscous hydroplaning (a thin film of water on a smooth surface prevents tire contact), and reverted rubber hydroplaning ( from a locked, tire trapped water to and reverts the rubber to its ).