abaculus

Century Dictionary and Cyclopedia

1. n. Literally, a small abacus. Specifically, one of the little cubes or slabs of colored glass, enamel, stone, or other material employed in mosaic work or in marquetry. Also called abaciscus.

Wiktionary

1. n. A small tile of glass, marble, or other substance, of various colors, used in making ornamental patterns in mosaic pavements. - Fairholt.
2. n. A small tile of glass, marble, or other substance, of various colors, used in making ornamental patterns in mosaic pavements. - Fairholt.

GNU Webster's 1913

1. n. A small tile of glass, marble, or other substance, of various colors, used in making ornamental patterns in mosaic pavements.