The Collaborative International Dictionary of English v.0.48:

Cooperation \Co*["o]p`er*a"tion\, n. [L. cooperatio: cf. F.
   coop['e]ration.]
   1. The act of cooperating, or of operating together to one
      end; joint operation; concurrent effort or labor.
      [1913 Webster]

            Not holpen by the cooperation of angels. --Bacon.
      [1913 Webster]

   2. (Polit. Econ.) The association of a number of persons for
      their benefit.
      [1913 Webster]

WordNet (r) 3.0 (2006):

cooperation
    n 1: joint operation or action; "their cooperation with us was
         essential for the success of our mission" [ant:
         competition, contention, rivalry]
    2: the practice of cooperating; "economic cooperation"; "they
       agreed on a policy of cooperation"