Source : Webster's Revised Unabridged Dictionary (1913)

Demonolatry \De`mon*ol"a*try\, n. [Gr. dai`mwn demon + latrei`a
   worship, ? to serve, worship: cf. F. d['e]monol[^a]trie.]
   The worship of demons.

Source : WordNet®

demonolatry
     n : worship of devils [syn: {diabolatry}, {devil-worship}]