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

Moby Thesaurus II by Grady Ward, 1.0:

50 Moby Thesaurus words for "bushwhack":
   ambush, assail, assault, astonish, attack, blitz, catch off-guard,
   catch unawares, come at, come down on, come from behind,
   come upon unexpectedly, crack down on, descend on, descend upon,
   do the unexpected, drop in on, fall on, fall upon, gang up on,
   go at, go for, harry, have at, hit, hit like lightning, jump,
   land on, lay at, lay hands on, lay into, light into, mug,
   pitch into, pounce upon, pound, pull up short, sail into, set on,
   set upon, spring a surprise, spring upon, strike, surprise,
   swoop down on, take by surprise, take short, take the offensive,
   take unawares, wade into