Source : Webster's Revised Unabridged Dictionary (1913)

Czar \Czar\ (z["a]r), n. [Russ. tsare, fr. L. Caesar C[ae]sar;
   cf. OPol. czar, Pol. car. ]
   A king; a chief; the title of the emperor of Russia. [Written
   also {tzar}

Source : WordNet®

czar
     n 1: a male monarch or emperor (especially of Russia prior to
          1917) [syn: {tsar}, {tzar}]
     2: a person having great power