sparking plug vs spark plug

sparking plug and spark plug both are nouns.

Word	Noun	Adjective	Verb	Adverb
sparking plug	Yes	No	No	No
spark plug	Yes	No	No	No

As nouns, sparking plug and spark plug are synonyms defined as:

sparking plug and spark plug: electrical device that fits into the cylinder head of an internal-combustion engine and ignites the gas by means of an electric spark

Other synonyms of sparking plug include plug.

sparking plug (noun)	spark plug (noun)
electrical device that fits into the cylinder head of an internal-combustion engine and ignites the gas by means of an electric spark	electrical device that fits into the cylinder head of an internal-combustion engine and ignites the gas by means of an electric spark