ball cock

or ballcock

noun

1. a device for regulating the supply of water in a tank, cistern, or the like, consisting essentially of a valve connected to a hollow floating ball which by its rise or fall shuts or opens the valve.

ball cock

noun

1. a device for regulating the flow of a liquid into a tank, cistern, etc, consisting of a floating ball mounted at one end of an arm and a valve on the other end that opens and closes as the ball falls and rises with the water level in the cistern

Word History and Origins

Origin of ball cock¹

First recorded in 1780–90