The Collaborative International Dictionary of English v.0.48:

Despotic \Des*pot"ic\, Despotical \Des*pot"ic*al\, a. [Gr.
   despotiko`s: cf. F. despotique.]
   Having the character of, or pertaining to, a despot; absolute
   in power; possessing and abusing unlimited power; evincing
   despotism; tyrannical; arbitrary. -- Des*pot"ic*al*ly, adv.
   -- Des*pot"ic*al*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

despotical
    adj 1: belonging to or having the characteristics of a despot
           [syn: despotic, despotical]