ˈwater-ˌhammer
1. An instrument used to illustrate the fact that in a vacuum liquids and solids fall at the same rate. It consists of a hermetically sealed tube exhausted of air and partly filled with water. When the tube is quickly reversed, the water falls on the end with a noise like that of a hammer.
| 1805 Nicholson's Jrnl. Nat. Philos. (80) XI. 217 The water⁓hammer. This instrument, which is made and sold by the glass-blowers and barometer-makers, consists of [etc.]. 1870 Tyndall Heat iv. §131. (ed. 4) 112 One effect of the withdrawal of the elastic buffer [i.e. the air] is, that the water falls with the sound of a solid body, and hence this instrument is called the water hammer. |
| attrib. 1881 Tyndall Floating Matter of Air iii. 147 A number of hermetically-sealed tubes charged with the same infusion..have maintained for more than a year..their water⁓hammer sound. |
2. Hydraulics. The concussion or sound of concussion of water in a pipe when its flow is suddenly stopped, or when live steam is admitted.
| 1891 Century Dict. 1910 Encycl. Brit. XIV. 67/1 [Hydraulics] If in a pipe through which water is flowing a sluice is suddenly closed so as to arrest the forward movement of the water, there is a rise of pressure... This action is termed water hammer or water ram. 1919 Blackw. Mag. Feb. 183/2 There came a bubbling roar from the vent..and then the clang of a heavy ‘water-hammer’ in the pipe as the tank filled. |
b. Path. water-hammer pulse, a jerky pulse with a full expansion, followed by a sudden collapse.
| 1899 Allbutt's Syst. Med. VI. 388 The well-known ‘water⁓hammer pulse’ or ‘pulse of unfilled arteries’ of aortic regurgitation. |
3. Surg. A metal hammer heated in boiling water, used to produce a blister by gently striking the skin.
| 1891 Century Dict. 1911 Webster. |