- In a fiendish manner; evilly, wickedly.
- 1832, Jedadiah Cleishbotham [pseudonym; Walter Scott], chapter X, in Tales of My Landlord, Fourth and Last Series. [...] In Four Volumes, volume I (Count Robert of Paris), Edinburgh: Printed [by Ballantyne and Company] for Robert Cadell; London: Whittaker and Co., OCLC 81177709, page 306:
- At a side door, reclined on a couch, two guards of the haram, with their naked swords grasped in their hands, and features, fiendishly contorted between sleep and dissolution, seemed to menace death to any who should venture to approach.
- 1884, Eliza R[oxcy] Snow Smith, chapter XXV, in Biography and Family Record of Lorenzo Snow, One of the Twelve Apostles of the Church of Jesus Christ of Latter-day Saints, Salt Lake City, Ut.: Deseret News Company, printers, OCLC 15497512, page 190:
- […] I was suddenly awakened by a savage looking fellow standing close to my bedside, ordering me and my companion to leave our bed forthwith or suffer the consequences; at the same time using the most blasphemous language, and uttering the most hideous oaths imaginable, while fiendishly striking his huge fists in close proximity to my face.
- 1929 October–December, Robert E[rvin] Howard, “Skull-Face”, in Weird Tales, Indianapolis, Ind.: Popular Fiction Pub. Co., OCLC 55045234; republished as Skull-Face, United Kingdom: Read Books, 2013, →ISBN, chapter 8 (Black Wisdom):
- The terrible spectacle drove for the instant all thought of rebellion from my mind. My very blood froze in my veins and I stood motionless. I heard Hassim laugh grimly behind me. The eyes in the cadaverous face blazed fiendishly at me and I blanched from the concentrated satanic fury in them.
- Extremely, very.
- 2009, Jeremy Duns, Free Agent, London: Simon & Schuster UK, →ISBN, page 78:
- Either the Russians are so fiendishly clever that they've managed to keep one of their agents running in this organization for over twenty years or they're so fiendishly clever that they're sending us false defectors to claim that they have.
- 2015, Samer Nashef, The Naked Surgeon: The Power and Peril of Transparency in Medicine, Melbourne, Vic.: Scribe, →ISBN:
- In this operation, veins or arteries are taken from various body parts and used to bypass blockages or narrowings in the coronary arteries, those fine, fiddly, yet fiendishly important vital suppliers to the heart muscle itself.
- 2017 October 27, Alex McLevy, “Making a Killing: The Brief Life and Bloody Death of the Post-Scream Slasher Revival”, in The A.V. Club, archived from the original on 5 March 2018:
in a fiendish manner