/ Dictionary / Index M merciless: Meaning and Definition of Find definitions for: mer•ci•less Pronunciation: (mûr'si-lis), [key] — adj. without mercy; having or showing no mercy; pitiless; cruel: a merciless critic. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: merciless (Thesaurus) merciful mercurate Related Content Daily Word Quiz: clairvoyant Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language