water hammer

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A banging noise heard in a water pipe following an abrupt alteration of the flow with resultant pressure surges.
2. n. A banging noise in steam pipes, caused by steam bubbles entering a cold pipe partially filled with water.

Century Dictionary and Cyclopedia

1. n. The concussion of a moving volume of water in a pipe or passage, caused by sudden stoppage of flow, as by the abrupt closing of a faucet.
2. n. The noise, resembling a blow of a hammer, caused by the presence of water in a steam-pipe when live steam is passed through it.
3. n. A philosophical toy consisting of a hermetically sealed tube from which the air has been exhausted and which contains some water. It is so called because the water strikes against the tube with a noise similar to that of a hammer, there being no air to impede its motion.
4. n. A metal hammer heated in a flame or in boiling water. Tapping the skin with this hammer for a few seconds will cause a blister. It is used as a counter-irritant or a mild cautery.

Wiktionary

1. n. A surge of pressure in a pipe carrying a fluid; especially the banging sound in a steam or hot water pipe caused by bubbles of air, or by an abrupt alteration of the flow.

GNU Webster's 1913

1. (Physics) 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.
2. A concussion, or blow, made by water in striking, as against the sides of a pipe or vessel containing it.
3. A metal hammer used when heated, as by dipping in hot water, to blister the skin, as for counterritation.

WordNet 3.0

1. n. the banging sound of steam in pipes