Water hammer : A vessel partly filled with water, exhausted of air, and hermetically sealed. When reversed or shaken, the water being unimpeded by air, strikes the sides in solid mass with a sound like that of a hammer.

Water hammer : A concussion, or blow, made by water in striking, as against the sides of a pipe or vessel containing it.

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Taxonomy
water hammer, pipe, valve, pipeline, the fluid, pressure wave, compressibility, liquid, check valve, gas, modulus, wave speed, modulus of elasticity, pressure, vessels, water hammer pulse, free encyclopedia, equation.

Defination from the web:
Water hammer can cause pipelines to break if the pressure is high enough. ... Other causes of water hammer are Pump failure, and Check valve slam (due to sudden deceleration, a check valve may slam shut rapidly, depending ...