The Collaborative International Dictionary of English v.0.48:

bushwhack \bush"whack`\ v. t.
   to lie in ambush for, lie in wait for.

   Syn: ambush, scupper, lie for, waylay, lurk, ambuscade.
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

bushwhack \bush"whack`\ v. i.
   1. to live in the bush as a fugitive or as a guerilla.
      [WordNet 1.5]

   2. to cut one's way through the woods or bush.
      [WordNet 1.5]

WordNet (r) 3.0 (2006):

bushwhack
    v 1: wait in hiding to attack [syn: ambush, scupper,
         bushwhack, waylay, lurk, ambuscade, lie in wait]
    2: live in the bush as a fugitive or as a guerilla
    3: cut one's way through the woods or bush