hierocracy

from WordNet (r) 3.0 (2006)

hierocracy
    n 1: a ruling body composed of clergy

from The Collaborative International Dictionary of English v.0.48

Hierocracy \Hi`er*oc"ra*cy\, n. [Gr. "iero`s sacred + ? to be
   strong, rule.]
   Government by ecclesiastics; a hierarchy. --Jefferson.
   Hieroglyph