Source : Webster's Revised Unabridged Dictionary (1913)

Counterplot \Coun`ter*plot"\ (koun`t?r-pl?t"), v. t. [imp. & p.
   p. {Counterplotted}; p. pr. & vb. n. {Counterplotting}.]
   To oppose, as another plot, by plotting; to attempt to
   frustrate, as a stratagem, by stratagem.

         Every wile had proved abortive, every plot had been
         counterplotted.                          --De Quinsey.

Counterplot \Coun"ter*plot`\ (koun"t?r-pl?t`), n.
   A plot or artifice opposed to another. --L'Estrange.

Source : WordNet®

counterplot
     n : a plot intended to subvert another plot [syn: {counterplan}]
     v : make a plot in response to another plot
     [also: {counterplotting}, {counterplotted}]