/ Dictionary / Index R ruthenium: Meaning and Definition of Find definitions for: ru•the•ni•um Pronunciation: (r-thē'nē-um, -thēn'yum), [key] — n. Chem. a steel-gray, rare metallic element, belonging to the platinum group of metals. Symbol: Ru; at. wt.: 101.07; at. no.: 44; sp. gr.: 12.2 at 20°C. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: ruthenium (Thesaurus) ruthenious Rutherford Related Content Daily Word Quiz: panacea Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language