tritheism

from WordNet (r) 3.0 (2006)

tritheism
    n 1: (Christianity) the heretical belief that the Father and the
         Son and the Holy Spirit are three separate gods

from The Collaborative International Dictionary of English v.0.48

Tritheism \Tri"the*ism\, n. [Pref. tri- + Gr. ? God: cf. F.
   trith['e]isme.]
   The opinion or doctrine that the Father, Son, and Holy Spirit
   are three distinct Gods.
   [1913 Webster]