coating vs overcoat

coating and overcoat both are nouns.

Word	Noun	Adjective	Verb	Adverb
coating	Yes	No	No	No
overcoat	Yes	No	No	No

As nouns, overcoat is a hyponym of coating; that is, overcoat is a word with a more specific, narrower meaning than coating:

coating (noun)	overcoat (noun)
the work of applying something	a heavy coat worn over clothes in winter
a thin layer covering something	an additional protective coating (as of paint or varnish)
a heavy fabric suitable for coats
a decorative texture or appearance of a surface (or the substance that gives it that appearance)