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[key-suh n, -son] /ˈkeɪ sən, -sɒn/
a structure used in underwater work, consisting of an airtight chamber, open at the bottom and containing air under sufficient pressure to exclude the water.
a boatlike structure used as a gate for a dock or the like.
  1. Also called camel, pontoon. a float for raising a sunken vessel, sunk beside the vessel, made fast to it, and then pumped out to make it buoyant.
  2. a watertight structure built against a damaged area of a hull to render the hull watertight; cofferdam.
a two-wheeled wagon, used for carrying artillery ammunition.
an ammunition chest.
a wooden chest containing bombs or explosives, used formerly as a mine.
Architecture, coffer (def 4).
1695-1705; < French, Middle French < Old Provençal, equivalent to caissa box (see case2) + -on augmentative suffix
Related forms
caissoned, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for caissons
  • The headworks will consist of reinforced concrete pile walls and bridge deck founded on drilled reinforced concrete caissons.
  • Concrete formwork for the bascule caissons is being built on-site.
  • Some of this ground water may come to the surface when the caissons are installed.
  • It also employs a mat foundation as a cost saving alternative to drilling deep caissons.
  • Constructs all basic foundation supports such as augured in place piling, drilled caissons and cast-in-place piling.
  • Detonators and explosives shall not be stored or kept in tunnels, shafts, or caissons.
  • The superstructure is supported by concrete spill-through piers, each of which rests on two steel caissons.
  • Upgrade existing wharf to improve its seismic resistance by strengthening the existing caissons.
  • Enormous steel caissons were sunk into the mud under the straits and then driven to bedrock.
  • Please provide what size and depth of these caissons need to be.
British Dictionary definitions for caissons


/kəˈsuːn; ˈkeɪsən/
a watertight chamber open at the bottom and containing air under pressure, used to carry out construction work under water
a similar unpressurized chamber
a watertight float filled with air, used to raise sunken ships See also camel (sense 2)
a watertight structure placed across the entrance of a basin, dry dock, etc, to exclude water from it
  1. a box containing explosives, formerly used as a mine
  2. an ammunition chest
  3. a two-wheeled vehicle containing an ammunition chest
another name for coffer (sense 3)
Word Origin
C18: from French, assimilated to caissecase²
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
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Word Origin and History for caissons



1704, from French caisson "ammunition wagon, box, crate," from Middle French caisson "large box" (16c.), from Italian cassone, augmentative form of cassa "a chest," from Latin capsa "a box" (see case (n.2)).

Online Etymology Dictionary, © 2010 Douglas Harper
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