The Collaborative International Dictionary of English v.0.48:
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. [1913 Webster] 2. A dynasty; a government. [Obs.] [1913 Webster]WordNet (r) 3.0 (2006):
dynast n 1: a hereditary ruler