The Collaborative International Dictionary of English v.0.48:

nonviolence \nonviolence\ n.
   The theory, doctrine, or practice of peaceful resistance to a
   government by fasting or refusing to cooperate.

   Syn: passive resistance.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

nonviolence
    n 1: peaceful resistance to a government by fasting or refusing
         to cooperate [syn: passive resistance, nonviolent
         resistance, nonviolence]

Moby Thesaurus II by Grady Ward, 1.0:

91 Moby Thesaurus words for "nonviolence":
   a wise passiveness, abnegation, abstinence, calm, calmness,
   conservatism, constraint, contemplation, contemplative life,
   continence, control, cool, dispassion, do-nothing policy,
   do-nothingism, do-nothingness, dormancy, evenness, gentleness,
   golden mean, happy medium, idleness, immobility, impartiality,
   inaction, inactivity, indolence, inertia, inertness, irenicism,
   judiciousness, juste-milieu, laissez-aller, laissez-faire,
   laissez-faireism, lenity, meden agan, meditation, middle way,
   mildness, moderateness, moderation, moderationism, neutralism,
   neutrality, neutralness, noninvolvement, nonparticipation,
   nonresistance, nonviolent resistance, nothing in excess, pacifism,
   paralysis, passive resistance, passive self-annihilation,
   passiveness, passivism, passivity, peaceableness,
   peaceful coexistence, policy, procrastination, prudence,
   quiescence, quietism, repose, restraint, self-abnegation,
   self-control, self-denial, self-restraint, serenity, sobriety,
   stability, stagnancy, stagnation, standpattism, stasis, steadiness,
   temperance, temperateness, tranquillity, unexcessiveness,
   unextravagance, unextremeness, unpugnaciousness, vegetation,
   via media, vita contemplativa, waiting game,
   watching and waiting