Source : Webster's Revised Unabridged Dictionary (1913)

Bushwhacking \Bush"whack`ing\, n.
   1. Traveling, or working a way, through bushes; pulling by
      the bushes, as in hauling a boat along the bushy margin of
      a stream. [U.S.] --T. Flint.

   2. The crimes or warfare of bushwhackers. [U.S.]

Source : WordNet®

bushwhacking
     adj : lying in ambush; "bushwhacking guerrillas attacking from
           ambush"