The Collaborative International Dictionary of English v.0.48:

Allotheism \Al"lo*the*ism\, n. [Gr. ? other + ? god.]
   The worship of strange gods. --Jer. Taylor.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "allotheism":
   acosmism, animatism, animism, anthropolatry, anthropomorphism,
   anthropotheism, autotheism, cosmotheism, deism, ditheism, dualism,
   dyotheism, heathendom, heathenism, heathenry, henotheism,
   hylotheism, idolatry, monolatry, monotheism, multitheism,
   myriotheism, pagandom, paganism, paganry, pantheism,
   physicomorphism, physitheism, polytheism, psychotheism,
   tetratheism, theism, theopantism, theriotheism, tritheism,
   zootheism