undercoat

definition: thick soft fur lying beneath the longer and coarser guard hair
example:
speech part: noun
synonyms: underfur
definition: the first or preliminary coat of paint or size applied to a surface
example:
speech part: noun
synonyms: priming
definition: seal consisting of a coating of a tar or rubberlike material on the underside of a motor vehicle to retard corrosion
example:
speech part: noun
synonyms: underseal
definition: cover with a primer
example:
speech part: verb
synonyms: prime ground

How undercoat is being used?