The Collaborative International Dictionary of English v.0.48:

Despotism \Des"po*tism\, n. [Cf. F. despotisme.]
   1. The power, spirit, or principles of a despot; absolute
      control over others; tyrannical sway; tyranny. "The
      despotism of vice." --Byron.
      [1913 Webster]

   2. A government which is directed by a despot; a despotic
      monarchy; absolutism; autocracy.
      [1913 Webster]

            Despotism . . . is the only form of government which
            may with safety to itself neglect the education of
            its infant poor.                      --Bp. Horsley.
      [1913 Webster]

WordNet (r) 3.0 (2006):

despotism
    n 1: dominance through threat of punishment and violence [syn:
         absolutism, tyranny, despotism]
    2: a form of government in which the ruler is an absolute
       dictator (not restricted by a constitution or laws or
       opposition etc.) [syn: dictatorship, absolutism,
       authoritarianism, Caesarism, despotism, monocracy,
       one-man rule, shogunate, Stalinism, totalitarianism,
       tyranny]