Source : Webster's Revised Unabridged Dictionary (1913)

Demonic \De*mo"nic\, a. [L. daemonicus, Gr. daimoniko`s.]
   Of or pertaining to a demon or to demons; demoniac. ``Demonic
   ambushes.'' --Lowell.

Source : WordNet®

demonic
     adj : extremely evil or cruel; expressive of cruelty or befitting
           hell; "something demonic in him--something that could
           be cruel"; "fires lit up a diabolic scene"; "diabolical
           sorcerers under the influence of devils"; "a fiendish
           despot"; "hellish torture"; "infernal instruments of
           war"; "satanic cruelty"; "unholy grimaces" [syn: {diabolic},
            {diabolical}, {fiendish}, {hellish}, {infernal}, {satanic},
            {unholy}]