The Collaborative International Dictionary of English v.0.48:

Quietism \Qui"et*ism\, n. [Cf. F. qui['e]tisme.]
   1. Peace or tranquillity of mind; calmness; indifference;
      apathy; dispassion; indisturbance; inaction.
      [1913 Webster]

   2. (Eccl. Hist.) The system of the Quietists, who maintained
      that religion consists in the withdrawal of the mind from
      worldly interests and anxieties and its constant
      employment in the passive contemplation of God and his
      attributes.
      [1913 Webster]

WordNet (r) 3.0 (2006):

quietism
    n 1: a form of religious mysticism requiring withdrawal from all
         human effort and passive contemplation of God

Moby Thesaurus II by Grady Ward, 1.0:

102 Moby Thesaurus words for "quietism":
   Quakerism, a wise passiveness, acquiescence, amenability, ataraxia,
   ataraxy, blank mind, blankmindedness, blankness, calm of mind,
   calmness, compliance, composure, contemplation, contemplative life,
   do-nothing policy, do-nothingism, do-nothingness, dormancy,
   emptiness of mind, empty-headedness, fallow mind, fatuity,
   foolishness, humbleness, humility, idleness, immobility,
   imperturbability, inaction, inactivity, inanity, indolence,
   inertia, inertness, laissez-aller, laissez-faire, laissez-faireism,
   lucid stillness, marmoreal repose, meditation, meekness,
   mental blankness, neutralism, neutrality, neutralness, nirvana,
   noninvolvement, nonparticipation, nonresistance, nonviolence,
   nonviolent resistance, obedience, oblivion, pacifism, paralysis,
   passive resistance, passive self-annihilation, passiveness,
   passivism, passivity, peace, peacefulness, placidity, placidness,
   policy, procrastination, quiescence, quiescency, quiet, quietness,
   quietude, repose, resignation, rest, restfulness, satori, serenity,
   silence, silken repose, sleep, slumber, stagnancy, stagnation,
   standpattism, stasis, stillness, submission, submissiveness,
   tabula rasa, thoughtfreeness, thoughtlessness, tranquillity,
   uncomplainingness, unintelligence, vacancy, vacuity, vegetation,
   vita contemplativa, waiting game, watching and waiting,
   wise passiveness