primer vs primer coat

primer and primer coat both are nouns.

Word	Noun	Adjective	Verb	Adverb
primer	Yes	No	No	No
primer coat	Yes	No	No	No

As nouns, primer and primer coat are synonyms defined as:

primer and primer coat: the first or preliminary coat of paint or size applied to a surface

Other synonyms of primer include flat coat, ground, priming, priming coat, undercoat.

primer (noun)	primer coat (noun)
any igniter that is used to initiate the burning of a propellant	the first or preliminary coat of paint or size applied to a surface
the first or preliminary coat of paint or size applied to a surface
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