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spark plug

a device designed to fit in each cylinder of a gasoline-powered internal-combustion engine and to produce the electric spark for igniting the mixture of gasoline and air.
Informal. a person who leads, inspires, or animates a group.
Origin of spark plug
1900-05 Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the Web for spark-plug
Historical Examples
  • As one of the wires to a spark-plug had broken, my engine was not running right, so I turned and went home.

  • Bless my spark-plug, but they might have imagined I had money.

    Tom Swift and his Airship Victor Appleton
  • In automobile-motors, however, the spark-plug only too often fails to perform its function.

  • This point will vary with different methods of ignition, as well as the location of the spark-plug or igniter.

    Aviation Engines Victor Wilfred Pag
  • He was just finishing with the spark-plug when the confidence of the air service boys received a sudden jolt.

  • Dirty or cracked insulator at spark-plug will cause short circuit and can only be detected by careful examination.

    Aviation Engines Victor Wilfred Pag
  • In a loop aerial, eight miles up, it might sound like a spark-plug, or it might sound like something else.

    Morale Murray Leinster
  • Prime cylinders by putting about a teaspoonful of gasoline in through pet cock or spark-plug opening.

    Aviation Engines Victor Wilfred Pag
  • However, on the exhaust stroke no spark is being generated in the magneto, hence none is produced at the spark-plug.

    Aviation Engines Victor Wilfred Pag
  • The other had just sighed with relief on completing the work of replacing the spark-plug that had become fouled with oil.

British Dictionary definitions for spark-plug

spark plug

another name for sparking plug
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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spark-plug in Science
spark plug  

A device in the cylinder head of an internal-combustion engine that ignites the fuel mixture by means of an electric spark. Spark plugs consist of two electrodes that are separated by an insulator except at their tips. When high voltage electricity is fed to one electrode, it jumps across the gap from one tip to the other as a spark. The voltage required to generate a spark is directly proportional to the size of the gap; in a car engine it is about 18,000 volts.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Slang definitions & phrases for spark-plug



To initiate and stimulate; trigger: Willy Mays sparked an eighth inning Giant drive by stealing second (1912+)

The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D.
Copyright (C) 2007 by HarperCollins Publishers.
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