Source : Webster's Revised Unabridged Dictionary (1913)

Kaiser \Kai"ser\, n. [Gr., fr. L. Caesar. Cf. {Kesar}, and
   {Czar}.]
   The ancient title of emperors of Germany assumed by King
   William of Prussia when crowned sovereign of the new German
   empire in 1871.

Source : WordNet®

Kaiser
     n : the title of the Holy Roman Emperors or the emperors of
         Austria or of Germany until 1918