regulator consisting of a small cock or faucet or valve for letting out air or releasing compression or draining
petcock详细解释
pet.cock n.（名词）A small valve or faucet used to drain or reduce pressure, as from a boiler.泄气阀，小龙头：用来排空或降低压力的一种小阀门或小龙头，如锅炉上的 来源：Perhaps pet 可能为 petcockcock
