noun
1. : a vessel (as a tube) partly filled with water, exhausted of air, and hermetically sealed so that when reversed or shaken the water strikes in solid mass with a sound like that of a hammer
2. : a concussion or sound of concussion of moving water against the sides of a containing pipe or vessel on a sudden stoppage of flow ; especially : such a concussion or sound made by water in a steam pipe
3. : the act or process of water-hammering