Source : Webster's Revised Unabridged Dictionary (1913)

Dynast \Dy"nast\, n. [L. dynastes, Gr. ?, fr. ? to be able or
   strong: cf. F. dynaste. See {Dynamic}.]
   1. A ruler; a governor; a prince.

   2. A dynasty; a government. [Obs.]

Source : WordNet®

dynast
     n : a hereditary ruler