The Collaborative International Dictionary of English v.0.48:

Militarism \Mil"i*ta*rism\, n. [Cf. F. militarisme.]
   [1913 Webster]
   1. A military state or condition; a military system; reliance
      on military force in administering government.
      [1913 Webster]

   2. The spirit and traditions of military life. --H. Spencer.
      [1913 Webster]

   3. The view that military strength, efficiency and values
      should dominate the country's public policy choices and
      take precedence over other interests.
      [1913 Webster PJC]

   4. The policy of maintaining a large military force, even in
      peacetime; -- a term usually used by opponents of such a
      policy on the assumption that such a large force is
      unnecessary for national defense.
      [PJC]

WordNet (r) 3.0 (2006):

militarism
    n 1: a political orientation of a people or a government to
         maintain a strong military force and to be prepared to use
         it aggressively to defend or promote national interests