/ Dictionary / Index H harmful: Meaning and Definition of Find definitions for: harm•ful Pronunciation: (härm'ful), [key] — adj. causing or capable of causing harm; injurious: a harmful idea; a harmful habit. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: harmful (Thesaurus) harmattan harmless Related Content Daily Word Quiz: fabricate Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language