Definitions

1. adjective

relating to or characteristic of a demon or demons; evil or wicked

“The demoniacal laughter echoed through the abandoned mansion.”

2. adjective

inspired by or characteristic of demons; diabolical

“The demoniacal plot to destroy the city was foiled by the authorities.”

3. noun

a person affected by demonic possession; a person exhibiting uncontrolled or violent behavior

“The doctor examined the patient, trying to determine if she was a demoniacal or just mentally unstable.”