spark plug

noun

1

: a part that fits into the cylinder head of an internal combustion engine and carries two electrodes separated by an air gap across which the current from the ignition system discharges to form the spark for combustion

2

: one that initiates or gives impetus to an undertaking

sparkplug

ˈspärk-ˌpləg 

transitive verb

Examples of spark plug in a Sentence

Recent Examples on the Web

Anyone who has tuned up a Tiger knows that to replace the rear-most spark plug on the driver’s side of a U.S.-spec car, the unfortunate mechanic must gain access through a plate on the interior firewall, or simply pull the engine. —Robert Ross, Robb Report, 22 Aug. 2025

The Dolphins clearly lucked out because there were long stretches of training camp where Gay, an undersized hybrid linebacker who is an emotional spark plug, made a flashy play (interception, sack, forced fumble, tackle for loss) every day. —Omar Kelly august 22, Miami Herald, 22 Aug. 2025

Backup guard Miles McBride, who has been a spark plug over the last couple of years, remains on the roster. —Robert Marvi, MSNBC Newsweek, 20 Aug. 2025

Anthony is more of a spark plug than a true lead guard. —Brian Sampson, Forbes.com, 31 July 2025

Word History

First Known Use

1903, in the meaning defined at sense 1

Rhymes for spark plug

• debug
• humbug
• prodrug
• unplug
• antidrug
• mealybug
• multidrug
• chug
• doug
• drug
• dug
• hug

Kids Definition

spark plug

noun

1

: a device used in an engine to produce a spark that ignites a fuel mixture

2

: one that begins something or drives something forward