water-hammer noun. ['wɔ:tǝhamǝ] E19.
[from WATER noun + HAMMER noun.]
1. An evacuated tube partly filled with water which falls on the end with a noise like that of a hammer when the tube is reversed, used to illustrate the fact that in a vacuum liquids and solids fall at the same rate. E19.

2. The (sound of) concussion or reverberation in a water pipe when the flow is suddenly stopped, when there is an airlock, or when steam is admitted. L19.

3. Medicine. Used attrib. to designate a jerky pulse with a full expansion followed by a sudden collapse. L19.

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