undercoat vs underfur

undercoat and underfur both are nouns.

Word	Noun	Adjective	Verb	Adverb
undercoat	Yes	No	Yes	No
underfur	Yes	No	No	No

As nouns, undercoat and underfur are synonyms defined as:

undercoat and underfur: thick soft fur lying beneath the longer and coarser guard hair

undercoat (noun)	underfur (noun)
thick soft fur lying beneath the longer and coarser guard hair	thick soft fur lying beneath the longer and coarser guard hair
the first or preliminary coat of paint or size applied to a surface
seal consisting of a coating of a tar or rubberlike material on the underside of a motor vehicle to retard corrosion

undercoat (verb)	underfur (verb)
cover with a primer; apply a primer to