noun a metallic alloy of a deep black color.
2. niello ·noun a piece of metal, or any other object, so decorated.
3. niello ·noun an impression on paper taken from an ancient incised decoration or metal plate.
4. niello ·noun the art, process, or method of decorating metal with incised designs filled with the black alloy.
5. niello ·add. ·noun an impression on paper taken from the engraved or incised surface before the niello alloy has been inlaid.