Source : Webster's Revised Unabridged Dictionary (1913)

Hydroplane \Hy"dro*plane\, v. i.
   Of a boat, to plane (see {Plane}, below).

Hydroplane \Hy"dro*plane\, n. [Pref. hydro-, 1 + plane.]
   1. A plane, or any of a number of planes, projecting from the
      hull of a submarine boat, which by being elevated or
      depressed cause the boat, when going ahead, to sink or
      rise, after the manner of an a["e]roplane.

   2. A projecting plane or fin on a gliding boat to lift the
      moving boat on top of the water; also, a gliding boat.

Source : WordNet®

hydroplane
     n 1: an airplane that can land on or take off from water; "the
          designer of marine aircraft demonstrated his newest
          hydroplane" [syn: {seaplane}]
     2: a speedboat that is equipped with hydrofoils that lift it so
        that it skims the water at high speeds; "the museum houses
        a replica of the jet hydroplane that broke the record"
        [syn: {hydrofoil}]

hydroplane
     v : glide on the water in a hydroplane [syn: {seaplane}]