/ Dictionary / Index R ruthless: Meaning and Definition of Find definitions for: ruth•less Pronunciation: (rth'lis), [key] — adj. without pity or compassion; cruel; merciless: a ruthless tyrant. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: ruthless (Thesaurus) ruthful rutilant 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