niello

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Any of several black metallic alloys of sulfur with copper, silver, or lead, used to fill an incised design on the surface of another metal.
2. n. A surface or object decorated with one of these alloys.
3. n. The art or process of ornamenting metal surfaces with one of these alloys.
4. v. To decorate or inlay with niello.

Century Dictionary and Cyclopedia

1. n. A design in black on a surface of silver, as that of a plaque, chalice, or any ornamental or useful object, formed by engraving the design and then filling up the incised furrows with an alloy composed of silver, copper, lead, crude sulphur, and borax, thus producing the effect of a black drawing on the bright surface. The process is of Italian origin, and is still extensively practised in Russia, where the finest niello is now produced. In many examples, conversely, the ground is cut out and inlaid with the black alloy, on which the design appears white or bright, as in the cut.
2. n. An impression taken from the engraved surface before the incised lines have been filled up. It is from such impressions, accidental or intentional, that the modern art of incised engraving on metal is held to have originated in the fifteenth century, in the shop of the Florentine goldsmith Finiguerra.
3. n. The dark compound used for such inlays in silver, made up of different alloys of sulphur, silver, copper, etc.
4. n. Inlaid work of the kind defined above.
5. To decorate by means of niello-work; treat with niello or by the niello process.

Wiktionary

1. n. Any of various black metal alloys, made of sulphur with copper, silver or lead, used to create decorative designs on other metals.

GNU Webster's 1913

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