Source : Webster's Revised Unabridged Dictionary (1913)

Counterbalance \Coun`ter*bal"ance\ (-b?l"ans), v. t. [imp. & p.
   p. {Counterbalanced} (-anst); p. pr. & vb. n.
   {Counterbalancing}.]
   To oppose with an equal weight or power; to counteract the
   power or effect of; to countervail; to equiponderate; to
   balance.

         The remaining air was not able to counterbalance the
         mercurial cylinder.                      --Boyle.

         The cstudy of mind is necessary to counterbalance and
         correct the influence of the study of nature. --Sir W.
                                                  Hamilton.

Source : WordNet®

counterbalancing
     adj : serving to equilibrate; "he added a counterbalancing weight"