water hammer
n.— «Storage and release of energy in the fluid also occurs during a phenomenon know as “water hammer.” Water hammer is the term used to describe the effect that occurs when the velocity of the fluid moving through a pipe suddenly changes. This change causes a pressure wave to propagate within the pipe. Under certain conditions, it can create a banging noise, similar to the noise made when beating a pipe with a hammer, hence the term water hammer. Not surprisingly, common symptoms of this problem are high noise levels, vibration and broken pipes.» —“Reducing Hydraulic System Noise” by Brendan Casey Machinery Lubrication Sept., 2006. (source: Double-Tongued Dictionary)
Further reading
It was a dark and stormy night. So begins the long and increasingly convoluted prose of Edwards Bulwer-Lytton’s best-known novel. Today the annual Bulwer-Lytton Contest asks contestants for fanciful first sentences that are similarly...
Ron in Gloverville, South Carolina, wonders about the phrase since hatchet was hammer, which some use to mean “for a long period of time,” as in My family has lived here since hatchet was hammer. Another phrase he’s heard indicating the same thing...