• synonyms


[spon-suh n]
  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. Aeronautics. a protuberance at the side of a flying-boat hull, designed to increase lateral stability in the water.
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Origin of sponson

First recorded in 1825–35; variant of expansion
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for sponson

Historical Examples of sponson

  • 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

  • A bomb exploded directly beneath the sponson, where the dead body had fallen.

    Life in a Tank

    Richard Haigh

  • His tun of a torso bulged roundly out in front of me like the sponson of a battleship.

    Yellowstone Nights

    Herbert Quick

  • An eager gunner endeavoured to pass one of the tanks, but his gun caught the sponson and slipped off into the mud.

    A Company of Tanks

    W. H. L. Watson

British Dictionary definitions for sponson


  1. navy an outboard support for a gun enabling it to fire fore and aft
  2. a semicircular gun turret on the side of a tank
  3. a float or flotation chamber along the gunwale of a boat or ship
  4. a structural projection from the side of a paddle steamer for supporting a paddle wheel
  5. a structural unit attached to a helicopter fuselage by fixed struts, housing the main landing gear and inflatable flotation bags
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Word Origin for sponson

C19: perhaps from expansion
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012