A bib, faucet, or short pipe, fitted with a turning stopper or plug for permitting or restraining the flow of a liquid or gas; a cock or valve for checking or regulating the flow of water, gas, etc
A main shutoff for water to a home from a municipal supply. Usually these valves exist in pairs, on outside the property boundary and one inside the property boundary
A stopcock is a tap on a pipe, which you turn in order to allow something to pass through the pipe or to stop it from passing through. a tap that controls the flow of a liquid or gas through a pipe