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A small valve or faucet used to drain or reduce pressure, as from a boiler.

[Perhaps pet + cock.]
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


(Mechanical Engineering) a small valve for checking the water level in a steam boiler or draining condensed steam from the cylinder of a steam engine
[C19: from pet1 or perhaps French pet, from péter to break wind + cock1]
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014



a small valve or faucet, as for draining off excess or waste material from the cylinder of an internal-combustion engine.
[1860–65; pet, perhaps < French pet (see petard) + cock1]
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.petcock - regulator consisting of a small cock or faucet or valve for letting out air or releasing compression or drainingpetcock - regulator consisting of a small cock or faucet or valve for letting out air or releasing compression or draining
regulator - any of various controls or devices for regulating or controlling fluid flow, pressure, temperature, etc.
Based on WordNet 3.0, Farlex clipart collection. © 2003-2012 Princeton University, Farlex Inc.
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References in periodicals archive ?
Model 3206 bleeder petcocks are accessible with unloader on trailer; petcock is readily accessible if system bleeding is required.
The fittings at the top and bottom are brass with a small petcock at the bottom for drainage.
I turned up the heat on my stove and prayed I had the petcock on just right--not too loose and not too tight.
If using a dial gauge, open the petcock. Heat the canner over high heat until steam escapes.
Heat the canner until steam escapes the vent in a continuous stream for 10 minutes, then place the petcock over the vent.
Other mandatory accessories include an internal fluorescent lamp, petcock and water faucet controls, duplex electrical outlet, and a manual speed controller.
If you're winterizing a boat, there are two ways to deal with drain petcocks. Th better one is to remove the entire petcock.
Open each air tank's petcock just long enough to drain the water, then close it.
Once the victim was stabilized, they surveyed the scene and determined that the bike ignition and electrical systems were damaged and closed the bike's fuel petcock to prevent leakage and possible fire.
At the bottom of the drum is a petcock and rubber tube affair, which is attached to a filling machine (similar in size and shape to an eight cylinder automotive engine block).
The airplane was leveled, the drain petcock was opened at the center fuel cell sump and one quart of fuel was drained.