From Longman Dictionary of Contemporary Englishspark plugˈspark plug (also sparking plug British English) noun [countable] TTCTEa part in a car engine that produces an electric spark to make the petrol mixture start burning
Examples from the Corpus
spark plug• The distance between them is like the gap of a spark plug.• He was a spark plug at the top of the lineup.• For the sake of the team, she is willing to be the spark plug.• Always remove the lead from the spark plug of petrol machines and unplug electric models before cleaning or servicing. 