ball cock

or ball·cock


noun

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.

Origin of ball cock

First recorded in 1780–90

Example sentences from the Web for ball cock

British Dictionary definitions for ball cock

ball cock

noun

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