undercoat

nouns

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

verbs

cover with a primer; apply a primer to
ground, prime, undercoat