fiend ‧ ish /ˈfiːndɪʃ/ BrE AmE adjective
1 . cruel and unpleasant:
a particularly fiendish practical joke
2 . very clever in an unpleasant way:
a fiendish plan
3 . extremely difficult or complicated:
several fiendish exam questions
—fiendishly adverb
—fiendishness noun [uncountable]