- a watertight temporary structure in a river, lake, etc., for keeping the water from an enclosed area that has been pumped dry so that a bridge foundation, dam, or pier may be constructed
- a watertight box or chamber attached to the side of a ship so that repairs can be made below the waterline
- an empty space serving as a protective barrier, as between two compartments of a ship
coffer + dam
See cofferdam in American Heritage Dictionary 4
- A temporary watertight enclosure that is pumped dry to expose the bottom of a body of water so that construction, as of piers, may be undertaken.
- A watertight chamber attached to the side of a ship to facilitate repairs below the water line.
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