/ Dictionary / Index D dioptase: Meaning and Definition of Find definitions for: di•op•tase Pronunciation: (dī-op'tās), [key] — n. a mineral, hydrous copper silicate, CuSiO&multiplydot;HO, occurring in emerald-green crystals. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. diopsimeter diopter Related Content Daily Word Quiz: loathe Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language