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

Moby Thesaurus II by Grady Ward, 1.0:

122 Moby Thesaurus words for "militarism":
   Eisenhower Doctrine, Monroe Doctrine, Nixon Doctrine,
   Truman Doctrine, absolute monarchy, aggression, aggressiveness,
   antagonism, appeasement, aristocracy, autarchy, autocracy,
   autonomy, balance of power, bellicism, bellicosity, belligerence,
   belligerency, brinkmanship, chauvinism, coalition government,
   coexistence, colonialism, combativeness, commonwealth, compromise,
   constitutional government, constitutional monarchy, containment,
   contentiousness, democracy, detente, deterrence, dictatorship,
   diplomacy, diplomatic, diplomatics, dollar diplomacy,
   dollar imperialism, dominion rule, duarchy, duumvirate, dyarchy,
   expansionism, federal government, federation, ferocity,
   feudal system, fierceness, fight, foreign affairs, foreign policy,
   garrison state, gerontocracy, good-neighbor policy, heteronomy,
   hierarchy, hierocracy, home rule, hostility, imperialism,
   internationalism, isolationism, jingoism, limited monarchy,
   manifest destiny, martial law, martialism, meritocracy, militancy,
   military government, mob rule, mobocracy, monarchy, nationalism,
   neocolonialism, neutralism, nonresistance, ochlocracy, oligarchy,
   open door, open-door policy, pantisocracy, patriarchate,
   patriarchy, peace offensive, peaceful coexistence, police state,
   preparedness, pugnaciousness, pugnacity, pure democracy,
   quarrelsomeness, regency, representative democracy,
   representative government, republic, saber rattling,
   self-determination, self-government, shirt-sleeve diplomacy,
   shuttle diplomacy, social democracy, spheres of influence,
   stratocracy, technocracy, the big stick, thearchy, theocracy,
   totalitarian government, totalitarian regime, tough policy,
   triarchy, triumvirate, truculence, tyranny, unfriendliness,
   unpeacefulness, warmongering, warpath, welfare state,
   world politics