The Collaborative International Dictionary of English v.0.48:

International \In`ter*na"tion*al\, a. [Pref. inter- + national:
   cf. F. international.]
   [1913 Webster]
   1. Between or among nations; pertaining to the intercourse of
      nations; participated in by two or more nations; common
      to, or affecting, two or more nations.
      [1913 Webster]

   2. Of or concerning the association called the International.
      [1913 Webster]

   3. Independent of national boundaries; common to all people;
      as, the atmosphere is an international resource; the
      international community of scholars.
      [PJC]

   International code (Naut.), a common system of signaling
      adopted by nearly all maritime nations, whereby
      communication may be had between vessels at sea.

   International copyright. See under Copyright.

   International law, the rules regulating the mutual
      intercourse of nations. International law is mainly the
      product of the conditions from time to time of
      international intercourse, being drawn from diplomatic
      discussion, textbooks, proof of usage, and from recitals
      in treaties. It is called public when treating of the
      relations of sovereign powers, and private when of the
      relations of persons of different nationalities.
      International law is now, by the better opinion, part of
      the common law of the land. Cf. Conflict of laws, under
      Conflict. --Wharton.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

International \In`ter*na"tion*al\, n. [Cf. F. internationale.]
   [1913 Webster]
   1. The International; an abbreviated from of the title of the
      International Workingmen's Association, the name of an
      association, formed in London in 1864, which has for
      object the promotion of the interests of the industrial
      classes of all nations.
      [1913 Webster]

   2. A member of the International Association.
      [1913 Webster]

WordNet (r) 3.0 (2006):

international
    adj 1: concerning or belonging to all or at least two or more
           nations; "international affairs"; "an international
           agreement"; "international waters" [ant: national]
    2: from or between other countries; "external commerce";
       "international trade"; "developing nations need outside help"
       [syn: external, international, outside(a)]
    n 1: any of several international socialist organizations

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "international":
   all-comprehending, all-comprehensive, all-covering, all-embracing,
   all-encompassing, all-filling, all-including, all-inclusive,
   all-pervading, allover, catholic, civic, civil, common, communal,
   cosmopolitan, country-wide, ecumenic, ecumenical, foreign,
   galactic, general, global, heaven-wide, national,
   nondenominational, nonsectarian, planetary, public, social,
   societal, state, supranational, total, universal, world-wide,
   worldwide



Bouvier's Law Dictionary, Revised 6th Ed (1856):

INTERNATIONAL. That which pertains to intercourse between nations.
International law is that which regulates the intercourse between, or the
relative rights of nations.