The Collaborative International Dictionary of English v.0.48:

Internationalism \In`ter*na"tion*al*ism\, n.
   1. The state or principles of international interests and
      intercourse.
      [1913 Webster]

   2. The doctrines or organization of the International.
      [1913 Webster]

WordNet (r) 3.0 (2006):

internationalism
    n 1: the doctrine that nations should cooperate because their
         common interests are more important than their differences
         [ant: nationalism]
    2: quality of being international in scope; "he applauded the
       internationality of scientific terminology" [syn:
       internationality, internationalism]

Moby Thesaurus II by Grady Ward, 1.0:

62 Moby Thesaurus words for "internationalism":
   Eisenhower Doctrine, Monroe Doctrine, Nixon Doctrine,
   Truman Doctrine, appeasement, balance of power, brinkmanship,
   catholicity, coexistence, colonialism, compromise, containment,
   cosmopolitanism, detente, deterrence, diplomacy, diplomatic,
   diplomatics, dollar diplomacy, dollar imperialism, ecumenicalism,
   ecumenicity, expansionism, foreign affairs, foreign policy,
   generality, generalization, globalism, globality,
   good-neighbor policy, imperialism, inclusiveness, independence,
   internationality, isolationism, manifest destiny, militarism,
   nationalism, nationality, nationhood, neocolonialism, neutralism,
   nonresistance, open door, open-door policy, peace offensive,
   peaceful coexistence, peoplehood, preparedness, self-determination,
   self-government, shirt-sleeve diplomacy, shuttle diplomacy,
   sovereign nationhood, sovereignty, spheres of influence, statehood,
   the big stick, tough policy, universality, world politics,
   worldwideness