diabolical

From diabolic +‎ -al.

• (UK) IPA^(key): [ˌdaɪəˈbɒlɪkəɫ]

• Audio (Southern England):

  (file)

• (US) IPA^(key): [ˌdaɪəˈbɑlɪkəɫ]

diabolical (comparative more diabolical, superlative most diabolical)

1. Of or concerning the devil: devilish, satanic.
   • 2021 January 1, Moncure Daniel Conway, Demonology And Devil-Lore, Volume 1 by Moncure Daniel Conway: Popular Books by Moncure Daniel Conway : All times Bestseller Demanding Books, BEYOND BOOKS HUB, →ISBN:

     […] the many diabolical names assigned to boiling springs and to torrents that become dangerously swollen. In California the boiling springs called 'Devil's Tea-kettle' and 'Devil's Mush-pot' repeat the 'Devil's Punch-bowls' of Europe […]

2. Extremely wicked or cruel.

   a diabolical plan

3. (slang) (Devilishly) cunning or devious.
4. (slang) Crazy, wild (sometimes especially due to being unexpected or surprising).