diabolic

/ˌdaɪəˈbɒlɪk/

Use the adjective diabolic to describe someone who acts in a terribly cruel way. A diabolic boy might pick up a cat by its tail and swing it around.

When people are diabolic, they're evil. The horrible dictator who has thousands of civilians killed commits a diabolic act, and people who abuse children are also diabolic. The bad guy in a fairy tale is always diabolic. You can use diabolic interchangeably with the slightly more common diabolical. Both words have a Greek root, diabolikos, which means "devilish" and comes from diabolus, or "devil."

Definitions of diabolic

1. adjective

   showing the cunning or ingenuity or wickedness typical of a devil
   “the cold calculation and diabolic art of some statesmen”

   synonyms: devilish, diabolical, mephistophelean, mephistophelian

   evil

   morally bad or wrong
2. adjective

   extremely evil or cruel; expressive of cruelty or befitting hell
   “fires lit up a diabolic scene”

   synonyms: demonic, diabolical, fiendish, hellish, infernal, satanic, unholy

   evil

   morally bad or wrong