Pronunciation: (spon'sun), [key]
1. a structure projecting from the side or main deck of a vessel to support a gun or the outer edge of a paddle box.
2. a buoyant appendage at the gunwale of a canoe to resist capsizing.
3. Aeron.a protuberance at the side of a flying-boat hull, designed to increase lateral stability in the water.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.