The Collaborative International Dictionary of English v.0.48:

Caesarism \C[ae]"sar*ism\ (s[=e]"z[~e]r*[i^]z'm), n. [Cf. F.
   C['e]sarisme.]
   A system of government in which unrestricted power is
   exercised by a single person, to whom, as C[ae]sar or
   emperor, it has been committed by the popular will;
   imperialism; also, advocacy or support of such a system of
   government.
   [1913 Webster]

   Note: This word came into prominence in the time of Napoleon
         III., as an expression of the claims and political
         views of that emperor, and of the politicians of his
         court.
         [1913 Webster]

WordNet (r) 3.0 (2006):

Caesarism
    n 1: 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]