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Synonyms

fiendish

American  
[feen-dish] / ˈfin dɪʃ /

adjective

  1. diabolically cruel and wicked.

fiendish British  
/ ˈfiːndɪʃ /

adjective

  1. of or like a fiend

  2. diabolically wicked or cruel

  3. informal extremely difficult or unpleasant

    a fiendish problem
"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Other Word Forms

  • fiendishly adverb
  • fiendishness noun

Etymology

Origin of fiendish

First recorded in 1520–30; fiend + -ish 1

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.