Source : Webster's Revised Unabridged Dictionary (1913)

Plutocracy \Plu*toc"ra*cy\, n. [Gr. ?; ? wealth + ? to be
   strong, to rule, fr.? strength: cf. F. plutocratie.]
   A form of government in which the supreme power is lodged in
   the hands of the wealthy classes; government by the rich;
   also, a controlling or influential class of rich men.

Source : WordNet®

plutocracy
     n : a political system governed by the wealthy people