petcock

n. small valve or faucet used used to drain off waste material or reduce pressure

A petcock is a small valve used to control the flow of liquid or gas. Although petcocks are used in a wide variety of applications, the following passage will describe one of the most common applications of the petcock which is the control of gasoline on a motorcycle engine.
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Noun
1. regulator consisting of a small cock or faucet or valve for letting out air or releasing compression or draining
(hypernym) regulator

petcock
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Eng: petcock
Urdu: تیل نکالنے والی ڈرم کی چھوٹی سی ٹونٹی ۔