Definition of "fiendishly"

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.

1832, Jedadiah Cleishbotham [pseudonym; Walter Scott], chapter X, in Tales of My Landlord, Fourth and Last Series. […], volume I (Count Robert of Paris), Edinburgh: […] [Ballantyne and Company] for Robert Cadell; London: Whittaker and Co., page 306

[…] 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.

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, page 190

It was hot there too; big flies buzzed fiendishly, and did not sting, but stabbed.

1899 February, Joseph Conrad, “The Heart of Darkness”, in Blackwood’s Edinburgh Magazine, volume CLXV, number M, New York, N.Y.: The Leonard Scott Publishing Company, […], part I, page 208

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.

1929 October–December, Robert E[rvin] Howard, “Skull-Face”, in Weird Tales, Indianapolis, Ind.: Popular Fiction Pub. Co.; republished as Skull-Face, United Kingdom: Read Books, 2013, chapter 8 (Black Wisdom)

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.

2009, Jeremy Duns, Free Agent, London: Simon & Schuster UK, page 78

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.

2015, Samer Nashef, The Naked Surgeon: The Power and Peril of Transparency in Medicine, Melbourne, Vic.: Scribe

Balancing horror and comedy is fiendishly difficult. The two rarely work well together, which is why the successes become so lauded (Evil Dead 2, An American Werewolf In London, Dead Alive).

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

These cross-border value calculations can get fiendishly complicated, says Jack Bobo, director of the University of Nottingham’s Food Systems Institute. Take the EU’s Farm-to -Fork Strategy, which aims to—among other things—ensure that a quarter of Europe’s farmland is organic and reduce fertilizer use by at least 20 percent by 2030. Hitting these goals will probably reduce environmental hidden costs in Europe, but it’s likely it will also end up reducing the overall productivity of European farms.

2023 November 6, Matt Reynolds, “The World's Broken Food System Costs $12.7 Trillion a Year”, in Wired‎