The term top-coat refers to a protective layer of paint, varnish or other coating that is applied as a finishing touch to a surface. Antonyms for top-coat would be words that describe the opposite of this process. Some words that can be considered antonyms for top-coat are "initial coat", "base coat", "primer", "undercoat", and "first coat".
These terms describe the first layer of coating that is applied before a top-coat is added to provide an added layer of protection or to enhance the surface's appearance. The use of primers and undercoats can improve the finish and durability of the final product.