Ni‐el″lo (?), n. [It. niello, LL. nigellum a black of blackish enamel, fr. L. nigellus, dim. of niger black. See Negro, and cf. Anneal.] 1. A metallic alloy of a deep black color.
2. The art, process, or method of decorating metal with incised designs filled with the black alloy.
3. A piece of metal, or any other object, so decorated.
4. An impression on paper taken from an ancient incised decoration or metal plate.