/ Dictionary / Index F fiendish: Meaning and Definition of Find definitions for: fiend•ish Pronunciation: (fēn'dish), [key] — adj. diabolically cruel and wicked. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: fiendish (Thesaurus) fiend fierce Related Content Daily Word Quiz: censure Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language