/ Dictionary / Index I iridium: Meaning and Definition of Find definitions for: i•rid•i•um Pronunciation: (i-rid'ē-um, ī-rid'-), [key] — n. Chem. a precious metallic element resembling platinum: used in platinum alloys and for the points of gold pens. Symbol: Ir; at. wt.: 192.2; at. no.: 77; sp. gr.: 22.4 at 20°C. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: iridium (Thesaurus) iridic iridize Related Content Daily Word Quiz: spectral Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language