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
First recorded in 1900–05
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for spark plug
Historical Examples of spark plug
Bless my spark-plug, but they might have imagined I had money.
The spark-plug electrodes may be easily set by means of the gauge attached to the screwdriver.
This point will vary with different methods of ignition, as well as the location of the spark-plug or igniter.
Dirty or cracked insulator at spark-plug will cause short circuit and can only be detected by careful examination.
Prime cylinders by putting about a teaspoonful of gasoline in through pet cock or spark-plug opening.
British Dictionary definitions for spark 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
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
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