A hydrant is the thick metal pipe standing on the street, often red or yellow, with a heavy cap on top. Firefighters open it so water from the city's pipes rushes into their hoses. When people say hydrant they almost always mean a fire hydrant — there is not really another everyday kind. You do not drink from it, and you are not meant to wash the car from it, even though films sometimes show that. The word started in American English and then travelled; speakers elsewhere still understand it at once. In a city, “the hydrant on the corner” is enough. It is a street object for fires, not a kitchen tap.