Source : Webster's Revised Unabridged Dictionary (1913)

Diabolism \Di*ab"o*lism\, n.
   1. Character, action, or principles appropriate to the devil.

   2. Possession by the devil. --Bp. Warburton.

Source : WordNet®

diabolism
     n : the worship of devils (especially Satan) [syn: {demonism}, {Satanism}]