/ Dictionary / Index M molybdenum: Meaning and Definition of Find definitions for: mo•lyb•de•num Pronunciation: (mu-lib'du-num), [key] — n. Chem. a silver-white metallic element, used as an alloy with iron in making hard, high-speed cutting tools. Symbol: Mo; at. wt.: 95.94; at. no.: 42; sp. gr.: 10.2. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: molybdenum (Thesaurus) molybdenous molybdenum disulfide Related Content Daily Word Quiz: placid Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language