I happened to read this sentence

Now two questions:

  1. Is ‘fiendishly’ an acceptable term though ‘fiend’ is common?
  2. What does the phrase ‘fiendishly complicated’ mean?

Drawing on the definition of ‘fiendish’: “(informal) extremely awkward or complex–a fiendish problem", I’d say the sentence sounds good. (= complicated in an awkward way).


You could say devilishly complicated and perhaps relate that to the expression ‘the devil is in the detail’ suggesting that the more you examine the detail, the more complicated it becomes.

Thank you, Alan, for the lucidity you have brought out. I consider the view of Eugene, too.