Stucco is a thickly applied coating formed by mixing powder with water to form a wet paste, which dries on site to form a preservative or decorative outer layer. It can vary in thickness, and may be colored in the mixture or painted after drying. It does not include simple paint or oil-based coatings.

Stucco can be applied smoothly or given various textures, some of which have special decorative or aesthetic properties. It can be applied directly to brick, concrete, cinder blocks, panels, boards, polystyrene insulation, or other materials. It is sometimes reinforced with wire or plastic mesh.

The coating forms on site over a backing rather than arriving as a finished rigid cladding panel. A smooth or textured finish, integral color, later painting, and optional mesh reinforcement do not change its stucco identity.