WordNet (r) 3.0 (2006):

fend off
    v 1: prevent the occurrence of; prevent from happening; "Let's
         avoid a confrontation"; "head off a confrontation"; "avert
         a strike" [syn: debar, forefend, forfend, obviate,
         deflect, avert, head off, stave off, fend off,
         avoid, ward off]

Moby Thesaurus II by Grady Ward, 1.0:

63 Moby Thesaurus words for "fend off":
   anticipate, avert, avoid, bar, beat back, beat off, block,
   brush off, chase, chase away, chase off, check, counter, cut,
   debar, deflect, deter, discourage, dishearten, dismiss, drive away,
   drive back, estop, exclude, fend, forbid, foreclose, forestall,
   help, hinder, hold at bay, hold off, keep at bay, keep from,
   keep off, obstruct, obviate, pack off, parry, preclude, prevent,
   prohibit, push back, put back, rebuff, rebut, refuse, reject,
   repel, repulse, rule out, save, send away, send off, send packing,
   snub, spurn, stave off, stop, thrust back, turn aside, turn back,
   ward off