/ Dictionary / Index O onyxis: Meaning and Definition of Find definitions for: o•nyx•is Pronunciation: (ō-nik'sis), [key] — n. Pathol. an ingrowing of a fingernail or toenail. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: onyxis (Thesaurus) onyx onyx marble Related Content Daily Word Quiz: nonchalant Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language