Demoniac \De*mo"ni*ac\, n.

1. A human being possessed by a demon or evil spirit; one whose faculties are directly controlled by a demon.

The demoniac in the gospel was sometimes cast into the fire. --Bates.

2. (Eccl. Hist.) One of a sect of Anabaptists who maintain that the demons or devils will finally be saved.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Demoniac \De*mo"ni*ac\, Demoniacal \Dem`o*ni"a*cal\ (?; 277), a. [L. daemoniacus, fr. daemon; cf. F. d['e]moniaque. 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.

Source: Webster's Revised Unabridged Dictionary (1913)