The Collaborative International Dictionary of English v.0.48:

Quiescence \Qui*es"cence\, Quiescency \Qui*es"cen*cy\, n. [L.
   quiescentia, fr. quiescens, p. pr.; cf. F. quiestence. See
   Quiesce.]
   The state or quality of being quiescent. "Quiescence, bodily
   and mental." --H. Spencer.
   [1913 Webster]

         Deeds will be done; -- while be boasts his quiescence.
                                                  --R. Browning.
   [1913 Webster]

WordNet (r) 3.0 (2006):

quiescence
    n 1: a state of quiet (but possibly temporary) inaction; "the
         volcano erupted after centuries of dormancy" [syn:
         dormancy, quiescence, quiescency]
    2: quiet and inactive restfulness [syn: quiescence,
       quiescency, dormancy, sleeping]

Moby Thesaurus II by Grady Ward, 1.0:

115 Moby Thesaurus words for "quiescence":
   a wise passiveness, abidingness, awful silence, changelessness,
   cold storage, constancy, contemplation, contemplative life, dead,
   dead of night, deathlike silence, do-nothing policy, do-nothingism,
   do-nothingness, doldrums, dormancy, durability, durableness,
   duration, endurance, firmness, fixedness, frozenness,
   golden silence, hardening, hibernation, hush, hush of night,
   idleness, immobility, immovability, immovableness, immutability,
   inaction, inactiveness, inactivity, inaudibility, indolence,
   inertia, inertness, intermission, interruption, invariability,
   invariableness, inveteracy, laissez-aller, laissez-faire,
   laissez-faireism, lastingness, latency, long standing,
   lucid stillness, lull, meditation, motionlessness, mum, neutralism,
   neutrality, neutralness, noiselessness, noninvolvement,
   nonparticipation, nonresistance, nonviolence,
   nonviolent resistance, pacifism, paralysis, passive resistance,
   passive self-annihilation, passiveness, passivism, passivity,
   peace, permanence, permanency, perpetualness, persistence,
   persistency, policy, procrastination, quiescency, quiet, quietism,
   quietness, quietude, rest, rigidity, silence, silentness,
   solemn silence, solidity, soundlessness, stability, stagnancy,
   stagnation, standing, standpattism, stasis, steadfastness, still,
   stillness, suspension, tacitness, taciturnity, tomblike silence,
   torpor, tranquillity, unchangeability, unchangingness,
   underactivity, vegetation, vita contemplativa, waiting game,
   watching and waiting, whisht