- noun a coat of fine hair under the main coat of some animals
- A coat of paint that improves the seal of wood or of a previous coat of paint, and provides a superior adhesive base for the top coat.
- A paint used as a base for enamel.
- A colored primer paint.
- noun a coat of paint or emulsion applied to a surface before a top coat is applied
- noun paint or emulsion designed to be used as an undercoat