Source : Webster's Revised Unabridged Dictionary (1913)

Demonism \De"mon*ism\, n. [Cf. F. d['e]monisme.]
   The belief in demons or false gods.

         The established theology of the heathen world . . .
         rested upon the basis of demonism.       --Farmer.

Source : WordNet®

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