/ Dictionary / Index M molybdenum disulfide: Meaning and Definition of Find definitions for: molyb'denum disul'fide Pronunciation: [key] a black crystalline powder, MoS, insoluble in water, used as a lubricant and as a hydrogenation catalyst. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. molybdenum molybdenum trioxide Related Content Daily Word Quiz: vertigo Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language