caisson

American  

[key-suhn, -son] / ˈkeɪ sən, -sɒn /

noun

1. 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.

2. a boatlike structure used as a gate for a dock or the like.

3. Nautical.

   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.

4. a two-wheeled wagon, used for carrying artillery ammunition.

5. an ammunition chest.

6. a wooden chest containing bombs or explosives, used formerly as a mine.

7. Architecture. coffer.

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caisson British  

/ ˈkeɪsən, kəˈsuːn /

noun

1. a watertight chamber open at the bottom and containing air under pressure, used to carry out construction work under water

2. a similar unpressurized chamber

3. a watertight float filled with air, used to raise sunken ships See also camel

4. a watertight structure placed across the entrance of a basin, dry dock, etc, to exclude water from it

5. 1. a box containing explosives, formerly used as a mine

   2. an ammunition chest

   3. a two-wheeled vehicle containing an ammunition chest

6. another name for coffer

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Other Word Forms

• caissoned
  adjective

Etymology

Origin of caisson

1695–1705; < French, Middle French < Old Provençal, equivalent to caissa box ( see case ²) + -on augmentative suffix

Example Sentences

See Examples For:

caisson

For years, members of the tiny preservation society — their ages now ranging from 60s to 80s — have flown out in helicopters, landing on the caisson.

From Los Angeles Times ● Oct. 26, 2025

A soldier, gingerly, with almost mechanical precision, removed the silver urn containing Megellas’s cremated remains from the caisson and carried it to the gravesite.

From Washington Post ● Sep. 6, 2022

“The caisson, which segments the dry dock and allows work to proceed simultaneously on multiple vessels, will also be opened to allow water to fill the entire dry dock.”

From Seattle Times ● Jun. 3, 2022

On November 11, 1921, the Unknown was placed on a horse-drawn caisson and carried in a procession through Washington, D.C. and across the Potomac River.

From Fox News ● Oct. 4, 2021

Moment ago there had been men moving all along the crest, men sitting and wandering and riding horses, artillery moving here and there, a wagon, a caisson.

From "The Killer Angels: The Classic Novel of the Civil War" by Michael Shaara