adj. 1. Possessed, produced, or influenced by a demon: demoniac creatures. 2. Of, resembling, or suggestive of a devil; fiendish: demoniac energy; a demoniacal fit. n. One who is or seems to be possessed by a demon. [Middle English demoniak, from Late Latin daemoniacus, from Greek *daimoniakos, from daimonios, of a spirit, from daimōn, divine power; see DEMON.] de′mo·nia·cal·ly adv. |
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