spark plug definition by Webster's New World
- an electrical device threaded into the cylinder of an internal-combustion engine to ignite the fuel mixture by producing timed sparks between electrodes
- Informal a person or thing that inspires, activates, or advances something
spark plug definition by American Heritage Dictionary
nounThe American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
- A device inserted in the head of an internal-combustion engine cylinder that ignites the fuel mixture by means of an electric spark.
- Informal One who gives life or energy to an endeavor.
cutaway viewA. terminal B. ceramic insulation C. center electrode D. gap E. ground electrode
spark plug - Science Definition
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.