undercoat in WordNet English dictionary

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

1. cover with a primer; apply a primer to
   prime  ground  undercoat