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Meaning of multistep hydroplane

mul'ti•step hy'droplane

Pronunciation: (mul'ti-step"), [key]
— Naut. Naut.
  1. a motorship having a flat bottom built as a series of planes inclined forward, the ship planing on each from stem to stern as its speed increases.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.