definition of
hydrofoil

[1] #1 hydrofoil n. [foil] a device consisting of a flat or curved piece (as a metal plate) so that its surface reacts to the water it is passing through; "the fins of a fish act as hydrofoils". wn

[2] #2 hydrofoil n. [hydroplane] a speedboat that is equipped with winglike structures 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". wn