/ Dictionary / Index M mercurial: Meaning and Definition of Find definitions for: mer•cu•ri•al Pronunciation: (mur-kyoor'ē-ul), [key] —n. a preparation of mercury used as a drug. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: mercurial (Thesaurus) mercurate mercurial barometer. 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