Source : Webster's Revised Unabridged Dictionary (1913)

Coact \Co*act"\, v. t. [L. coactare, intens. fr. cogere,
   coactum, to force. See {Cogent}.]
   To force; to compel; to drive. [Obs.]

         The faith and service of Christ ought to be voluntary
         and not coacted.                         --Foxe.

Coact \Co*act"\, v. i. [Pref. co- + act, v. i.]
   To act together; to work in concert; to unite. [Obs.]

         But if I tell you how these two did coact. --Shak.

Source : WordNet®

coact
     v : act together, as of organisms