di·a·bol·i·cal 
(dī′ə-bŏlĭ-kəl) also di·a·bol·ic (-ĭk)
(dī′ə-bŏlĭ-kəl) also di·a·bol·ic (-ĭk)adj.
1. Of, concerning, or characteristic of the devil; satanic.
2. Appropriate to a devil, especially in degree of wickedness or cruelty.
[From Middle English deabolik, from Old French diabolique, from Late Latin diabolicus, from Latin diabolus, devil; see DEVIL.]
di′a·boli·cal·ly adv.
di′a·boli·cal·ness n.