<p><strong>Noun</strong></p><ul><li>a variety of chalcedony having straight parallel bands of alternating colors.</li><li>(not used technically) an unbanded chalcedony dyed for ornamental purposes.</li><li>black, especially a pure or jet black: The pelt of this animal can range from onyx to light brown, depending on the season.</li><li>a nail of a finger or toe.</li></ul><p><strong>Adjective</strong></p><ul><li>made of or set with banded chalcedony: He wore the onyx cufflinks she had given him for his birthday.</li><li>black, especially jet black: She was a vision in black, from her onyx hair to her shiny boots.</li></ul>