The Collaborative International Dictionary of English v.0.48:

Demoniacally \Dem`o*ni"a*cal*ly\, adv.
   In a demoniacal manner.
   [1913 Webster]

WordNet (r) 3.0 (2006):

demoniacally
    adv 1: in a very agitated manner; as if possessed by an evil
           spirit [syn: demoniacally, frenetically]