A primer coat serves as a preparatory layer for paint or other coating applications. Synonyms for primer coat include base coat, undercoat, foundation coat, ground coat, seal coat, and first coat. A base coat is the first layer of coating applied to a surface, while an undercoat is a layer applied between the surface and final coat to improve adhesion and coverage. A foundation coat is typically applied to prevent the surface color from bleeding through the final coat. A ground coat is a layer of paint or coating used as a base for decorative finishes like metallic or pearl effects. A seal coat is applied to porous surfaces to seal them before applying other coatings, and a first coat refers to the initial layer that is applied.