cofferdam

1. (engineering) A temporary watertight enclosure used to create a dry foundation for building bridges and other structures over water.Examples: "He stood full six feet in height, with noble shoulders, and a chest like a coffer-dam."; "Downstream there was a small wooden cofferdam and when he woke there were naked children splashing in the pool there and he rose and wrapped his jacket about his waist and walked out along the bank where he could sit and watch them."; "At fixed injection volume of PVC gels solution, the curvature of MLAs [(microlens arrays)] obtained with patterned electrode substrates at fixed sizes of cofferdam can be tuned by changing the preparation voltage."

2. (nautical) An empty space that acts as a protective barrier between two floors or bulkheads on a ship.

3. (introduced by dentist Sanford Christie Barnum, New York, in 1864, but after his century maintained only in other languages than English) A rubber dam to keep the teeth dry when operating upon them.Examples: "I refer to Dr. Barnum, who has given us the coffer-dam. I cannot detain you while I describe the immense benefit which his application of a very simple material has conferred on the public."; "Dr. La Roche then first we are informed made the claim that he knew of and used rubber for a coffer dam prior to Barnum."New-York