demoniacal /ˌdiːməˈnaɪəkəl/ adjective1 •Pertaining to, characteristic of, or produced by a demon or evil spirit; devilish, demonic, fiendish.Rebecca laughed in her face, with a horrid sarcastic demoniacal laughter, that almost sent the schoolmistress into fits. — 1847 formsmore demoniacal · most demoniacal