Source : Webster's Revised Unabridged Dictionary (1913)

Polytheistic \Pol`y*the*is"tic\, Polytheistical
\Pol`y*the*is"tic*al\, a.
   Of or pertaining to polytheism; characterized by polytheism;
   professing or advocating polytheism; as, polytheistic
   worship; a polytheistic author, or nation. --
   {Pol`y*the*is"tic*al*ly}, adv.

Source : WordNet®

polytheistic
     adj : worshipping or believing in more than one god [ant: {monotheistic}]