Source : Webster's Revised Unabridged Dictionary (1913)

Theism \The"ism\ (th[=e]"[i^]z'm), n. [NL. & E. thea tea +
   -ism.] (Med.)
   The morbid condition resulting from the excessive use of tea.

Theism \The"ism\, n. [From Gr. ? God; probably akin to ? to pray
   for, ? spoken by God, decreed: cf. F. th['e]isme. Cf.
   {Enthusiasm}, {Pantheon}, {Theology}.]
   The belief or acknowledgment of the existence of a God, as
   opposed to {atheism}, {pantheism}, or {polytheism}.

Source : WordNet®

theism
     n : the doctrine or belief in the existence of a God or gods
         [ant: {atheism}]