petcock

noun

Etymology: Apparently from pet + cock, because of its size.

1. A small valve, spout, or faucet operated by hand, usually used to release pressure or drain fluid.

   “The doctor placed the rubber mask over her face and turned a dial and I watched Catherine breathing deeply and rapidly. Then she pushed the mask away. The doctor shut off the petcock.”

   “The shutoff valve (petcock) is usually located on the gas pipe on the supply side of the meter.”