/ Dictionary / Index O osmium tetroxide: Meaning and Definition of Find definitions for: os'mium tetrox'ide Pronunciation: [key] — Chem. Chem. a crystalline or amorphous, colorless, poisonous compound, OsO, soluble in water, alcohol, and ether: used for microscopic staining, in photography, and as a catalyst in organic synthesis. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. osmium osmo- Related Content Daily Word Quiz: resilient Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language