Definition of spark plug noun from the Oxford Advanced Learner's Dictionary

 

spark plug

 noun
noun
BrE
 
; NAmE
 
(also plug)(British English also sparking plug) Parts of a car
 
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a part in a car engine that produces a spark (= a flash of electricity) which makes the fuel burn and starts the engine See related entries: Parts of a car
See the Oxford Advanced American Dictionary entry: spark plug