- 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
See spark plug in American Heritage Dictionary 4
- 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.
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cutaway view A. terminal B. ceramic insulation C. center electrode D. gap E. ground electrode
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