/ Dictionary / Index M mercapto: Meaning and Definition of Find definitions for: mer•cap•to Pronunciation: (mur-kap'tō), [key] — adj. Chem. containing the mercapto group; sulfhydryl; thiol. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. mercaptide mercapto group Related Content Daily Word Quiz: perspicacious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language