adj
fiendish
FEEN-dihsh
adj
1
Extremely cruel or wicked, as if inspired by a demon.
"The kidnappers hatched a fiendish plot to avoid detection."
2
Very difficult or intricate, especially in a way that seems almost deliberately cruel.
"The exam included one fiendish question that stumped almost everyone."
How to Use Fiendish
Learner’s notesIn plain EnglishDevilishly evil, or (more casually) devilishly hard.
Common pairings
a fiendish plan
a fiendish puzzle
Word Forms
more fiendish comparative, most fiendish superlative
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The kidnappers hatched a _____ plot to avoid detection.
Etymology
From fiend plus -ish.