Source : Webster's Revised Unabridged Dictionary (1913)

Cooperate \Co*["o]p"er*ate\, v. i. [imp. & p. p.
   {Co["o]perated}; p. pr. & vb. n. {Co["o]perating}.] [L.
   co["o]peratus, p. p. of co["o]perari to co["o]perate; co +
   operari to work, opus work. See {Operate}.]
   To act or operate jointly with another or others; to concur
   in action, effort, or effect.

         Whate'er co["o]perates to the common mirth. --Crashaw.