De*mo"ni*ac [L. daemoniacus, fr. daemon; cf. F. d'emoniaque. See Demon.]
1.
Pertaining to, or characteristic of, a demon or evil spirit; devilish; as, a demoniac being; demoniacal practices.
Sarcastic, demoniacal laughter.
Thackeray.
2.
Influenced or produced by a demon or evil spirit; as, demoniac or demoniacal power.
"
Demoniac frenzy."
Milton.
© Webster 1913.