spark plug

noun

Definition of spark plug

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

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In most cases, the metal is melted using an electrical arc, like in spark plugs. — Nicholas Wicks, Popular Mechanics, "Tool Test: What's the Best Entry-Level Welder?," 23 Dec. 2017 There also is a pretty simple explanation of how the spark plug ended up inside the formation. — Erik Lacitis, The Seattle Times, "Proof of alien visitors? Artifact from an ancient civilization? The truth is out there — in Seattle," 1 Dec. 2018 But the Supreme Court hasn’t adjudicated a vertical merger since 1972 when a majority blocked Ford’s acquisition of a spark plug manufacturer. — The Editorial Board, WSJ, "Trump’s Merger Appeal to Obama," 13 July 2018 Aside from a new gas tank, spark plugs, wires, fuel pump, fuel filter, air filter and fuel sending unit, the car is all-original and the replaced parts have been preserved and are included with the sale. — Gary Gastelu, Fox News, "1987 Buick Grand National parked since 1991 up for auction with 74 miles on it," 25 Sep. 2018 Clarkson is an offensive spark plug, averaging 14.5 points and 1.3 three-pointers per game this season. — Mike Barner, SI.com, "Fantasy Fallout of the Wild NBA Trade Deadline," 9 Feb. 2018 The senior guard hasn't been at 100% while dealing with a turf toe injury, but he's been a warrior and the spark plug during the Red Raiders' advancement. — Scott Gleeson, USA TODAY, "NCAA tournament Sweet 16: Most important players for every March Madness team," 20 Mar. 2018 Shane Victorino, a Rule 5 draft pick who became the spark plug of a World Series champion, plans to retire next month after signing a one-day contract with the Phillies. — Matt Breen, Philly.com, "Shane Victorino to sign one-day contract, retire as a Phillie in August celebration," 3 July 2018 The Ecuadorian spark plug tallied the decisive score on a penalty kick in the 78th minute, inching the ball past United keeper David Ousted’s outstretched arms into the top-right pocket. — Owen Pence, BostonGlobe.com, "Revolution hold off D.C. United," 1 July 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'spark plug.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.