Source : Webster's Revised Unabridged Dictionary (1913)

Pentarchy \Pen"tar*chy\, n. [Gr. ?: cf. F. pentarchie. See
   {Penta-}, and {-archy}.]
   A government in the hands of five persons; five joint rulers.
   --P. Fletcher. ``The pentarchy of the senses.'' --A. Brewer.