from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun Any of several structures that project from the side of a boat or ship, especially a gun platform.
  • noun A short, curved, air-filled projection on the hull of a seaplane, imparting stability in the water.

from The Century Dictionary.

  • noun Nautical, the curve of the timbers and planking toward the outer part of the wing, before and abaft each of the paddle-boxes of a steamer; also, the framework itself.
  • noun In a war-ship, a projecting structure in which a gun is placed: designed to enable the gun to be trained forward and aft.
  • In ship-building, to be fitted with a sponson, or to have a projection from the side of a vessel of the form of a sponson: usually followed by out.

from the GNU version of the Collaborative International Dictionary of English.

  • noun One of the triangular platforms in front of, and abaft, the paddle boxes of a steamboat.
  • noun One of the slanting supports under the guards of a steamboat.
  • noun One of the armored projections fitted with gun ports, used on modern war vessels.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun A projection from the side of a watercraft.


from The American Heritage® Dictionary of the English Language, 4th Edition

[Perhaps alteration of expansion.]


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  • We helped them up the ladder to a sponson where a shower was rigged.

    Never Forgotten Newsletter 2009

  • Nothing anyone can do now will change that. sponson Says:

    Matthew Yglesias » Fighting Them Over There 2007

  • The M3 itself had been a massive compromise with the mounting of its main gun in a side sponson that provided only limited tra - verse.

    Steel Victory Yeide, Harry 2003

  • Even worse, all of the AP rounds were in the hull sponson racks, and Fleig had to turn his turret away from the target in order for the crew to pass the ammo up.

    Steel Victory Yeide, Harry 2003

  • She led the way down the passageway to a sponson, an open-air enclosed area low on the ship.

    Hellfire Douglass, Keith 2002

  • ` During the day the smoking '-- is it called sponson.

    The Kinder, Gentler Military: Can America's Gender-Neutral Fighting Force Still Win Wars? 2000

  • There he lay, along one side of the tank between the engine and the sponson.

    Life in a Tank Richard Haigh

  • McKnutt signalled to him, and he opened fire from his sponson.

    Life in a Tank Richard Haigh

  • The tanks moved down to the temporary tankdrome which had been decided upon near the railway, and the sponson trucks were towed there.

    Life in a Tank Richard Haigh

  • We had the utmost difficulty in making the bolt-holes fit, and as each sponson weighs about three tons they were not easy to move and adjust.

    Life in a Tank Richard Haigh


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  • Are there any lists of ship-building terms?

    March 18, 2011

  • The problem might call for protection

    Or supplying a buoyant connection,

    So vessels will spawn some

    Odd type of sponson,

    A useful but awkward projection.

    April 11, 2015