Source : Webster's Revised Unabridged Dictionary (1913)

Theist \The"ist\, n. [Cf. F. th['e]iste. See {Theism}.]
   One who believes in the existence of a God; especially, one
   who believes in a personal God; -- opposed to {atheist}.

Source : WordNet®

theist
     adj : of or relating to theism [syn: {theistical}, {theistic}]

theist
     n : one who believes in the existence of a god or gods