—n. 1. a seaplane.
2. an attachment to an airplane enabling it to glide on the water.
3. a light, high-powered boat, esp. one with hydrofoils or a stepped bottom, designed to plane along the surface of the water at very high speeds.
4. a horizontal rudder for submerging or elevating a submarine.
—v.i. 1. to skim over water in the manner of a hydroplane.
2. to travel in a hydroplane.
3. Also,aquaplane.(of a vehicular tire or vehicle) to ride on a film of water on a wet surface with a resulting decrease in braking and steering effectiveness.