un·der·coat /-ˌkot/
  短毛,絨毛,內層油漆
  Un·der·coat n.
  1. A coat worn under another; a light coat, as distinguished from an overcoat, or a greatcoat.
  2. A growth of short hair or fur partially concealed by a longer growth; as, a dog's undercoat.
  ◄ ►
  undercoat
       n 1: seal consisting of a coating of a tar or rubberlike material
            on the underside of a motor vehicle to retard corrosion
            [syn: underseal]
       2: the first or preliminary coat of paint or size applied to a
          surface [syn: flat coat, ground, primer, priming,
          primer coat, priming coat]
       3: thick soft fur lying beneath the longer and coarser guard
          hair [syn: underfur]
       v : cover with a primer; apply a primer to [syn: prime, ground]