The Collaborative International Dictionary of English v.0.48:

Countersway \Coun"ter*sway`\ (-sw[=a]`), n.
   A swaying in a contrary direction; an opposing influence.
   [Obs.]
   [1913 Webster]

         A countersway of restraint, curbing their wild
         exorbitance.                             --Milton.
   [1913 Webster]