The Collaborative International Dictionary of English v.0.48:

Despot \Des"pot\, n. [F. despote, LL. despotus, fr. Gr.
   despo`ths master, lord, the second part of which is akin to
   po`sis husband, and L. potens. See Potent.]
   1. A master; a lord; especially, an absolute or irresponsible
      ruler or sovereign.
      [1913 Webster]

            Irresponsible power in human hands so naturally
            leads to it, that cruelty has become associated with
            despot and tyrant.                    --C. J. Smith.
      [1913 Webster]

   2. One who rules regardless of a constitution or laws; a
      tyrant.
      [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

25 Moby Thesaurus words for "despot":
   Simon Legree, absolute monarch, absolute ruler, all-powerful ruler,
   arrogator, autarch, autocrat, caesar, commissar, czar, dictator,
   disciplinarian, driver, duce, hard master, martinet, oligarch,
   oppressor, pharaoh, slave driver, stickler, strong man, tyrant,
   usurper, warlord