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

  • n. Nautical A timber or girder fastened above and parallel to the keel of a ship or boat for additional strength.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. A longitudinal beam fastened on top of the keel of a vessel for strength and stiffness.

from the GNU version of the Collaborative International Dictionary of English

  • n. A piece of timber in a ship laid on the middle of the floor timbers over the keel, and binding the floor timbers to the keel; in iron vessels, a structure of plates, situated like the keelson of a timber ship.

from The Century Dictionary and Cyclopedia

  • n. A line of jointed timbers in a ship laid on the middle of the floor-timbers over the keel, fastened with long bolts and clinched, thus binding the floor-timbers to the keel; in iron ships, a combination of plates corresponding to the keelson-timber of a wooden vessel. See cut under keel.
  • n. In iron ship-building, a longitudinal reinforcement of plates and bars in the interior of the vessel above the framing in the bottom.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. a longitudinal beam connected to the keel of ship to strengthen it


Alteration (influenced by keel1) of Middle English kelswin, probably from Old Norse *kjölsvīn : kjölr, keel + svīn, swine, timber.
(American Heritage® Dictionary of the English Language, Fourth Edition)
First attested from 1611. Compare with Dutch kolzwijn, kolsem, Low German, kielswîn, German Kielschwein, Danish kølsvin, kölsvin, all with the same meaning. First part is keel while the second part is uncertain; possibly sill. (Wiktionary)



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  • What do we plant when we plant the tree?
    We plant the ship which will cross the sea.
    We plant the mast to carry the sails;
    We plant the planks to withstand the gales -
    The keel, the keelson, the beam, the knee;
    We plant the ship when we plant the tree.

    - Henry Abbey, 'What Do We Plant?'

    November 12, 2008

  • "We had better be going together over the ship, Captain," said the senior partner; and the three men started to view the perfections of the Nan-Shan from stem to stern, and from her keelson to the trucks of her two stumpy pole-masts.

    - Conrad, Typhoon

    March 26, 2008

  • "...they had of course scoured the frigate from truck to keelson..."
    --Patrick O'Brian, The Thirteen Gun Salute, 206

    March 4, 2008