The Collaborative International Dictionary of English v.0.48:

nonviolent \nonviolent\ adj.
   1. peacefully resistant in response to injustice; not using
      violence; -- used of protests and demonstrations; as,
      nonviolent resistance. Opposite of violent.

   Syn: passive, peaceful.
        [WordNet 1.5]

   2. achieved without bloodshed. Contrasted with bloody.

   Syn: unbloody, bloodless.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

nonviolent
    adj 1: abstaining (on principle) from the use of violence [ant:
           violent]
    2: achieved without bloodshed; "an unbloody transfer of power"
       [syn: nonviolent, unbloody]

Moby Thesaurus II by Grady Ward, 1.0:

30 Moby Thesaurus words for "nonviolent":
   bland, civilian, conciliatory, dovish, gentle, irenic, judicious,
   mild, mild as milk, moderate, nonaggressive, noncombatant,
   nonmilitant, pacific, pacificatory, pacifist, pacifistic,
   peace-loving, peaceable, peaceful, prudent, sober, soft, tame,
   temperate, unbellicose, uncontentious, unhostile, unmilitant,
   unmilitary