Pronunciation: (on'iks, ō'niks), [key]
1. Mineral.a variety of chalcedony having straight parallel bands of alternating colors. Cf. Mexican onyx.
2. (not used technically) an unbanded chalcedony dyed for ornamental purposes.
3. black, esp. a pure or jet black.
4. Med.a nail of a finger or toe.
black, esp. jet black.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.