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cais·son (kāsŏn, -sən)
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n.
1. A watertight structure within which construction work is carried on under water.
2. See camel.
3. A large box open at the top and one side, designed to fit against the side of a ship and used to repair damaged hulls under water. Also called cofferdam.
4. A floating structure used to close off the entrance to a dock or canal lock.
5.
a. A horse-drawn vehicle, usually two-wheeled, used to carry artillery ammunition in warfare or to bear a coffin at a military funeral.
b. A large box used to hold ammunition.

[French, from Old French, large box, alteration (influenced by caisse, chest) of casson, from Italian cassone, augmentative of cassa, box, from Latin capsa.]
(click for a larger image)
caisson
escorting the coffin of President Ronald Reagan to the US Capitol Rotunda in 2004

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
 

Indo-European & Semitic Roots Appendices

    Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:

    Indo-European Roots

    Semitic Roots

    The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.

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