ADJECTIVE (4)

1. not active or activated;
- Example: "the quiescent level of centimeter wave-length solar radiation"

2. marked by a state of tranquil repose;
- Example: "the quiescent melancholy of the town"

3. being quiet or still or inactive;

4. (pathology) causing no symptoms;
- Example: "a quiescent tumor"

The Collaborative International Dictionary of English v.0.48:

Quiescent \Qui*es"cent\, a. [L. quiescens, -entis, p. pr. of
   quiescere: cf. F. quiescent. See Quiesce.]
   1. Being in a state of repose; at rest; still; not moving;
      as, a quiescent body or fluid.
      [1913 Webster]

   2. Not ruffed with passion; unagitated; not in action; not
      excited; quiet; dormant; resting.
      [1913 Webster]

            In times of national security, the feeling of
            patriotism . . . is so quiescent that it seems
            hardly to exist.                      --Prof.
                                                  Wilson.
      [1913 Webster]

   3. (Gram.) Not sounded; silent; as, y is quiescent in "day"
      and "say."
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Quiescent \Qui*es"cent\, n. (Gram.)
   A silent letter. --M. Stuart.
   [1913 Webster]

WordNet (r) 3.0 (2006):

quiescent
    adj 1: not active or activated; "the quiescent level of
           centimeter wave-length solar radiation"
    2: marked by a state of tranquil repose; "the quiescent
       melancholy of the town"
    3: being quiet or still or inactive
    4: (pathology) causing no symptoms; "a quiescent tumor"

Moby Thesaurus II by Grady Ward, 1.0:

125 Moby Thesaurus words for "quiescent":
   abeyant, abiding, at a standstill, at rest, calm, changeless,
   cloistered, constant, contemplative, continuing, cool, do-nothing,
   dormant, durable, dwindling, ebbing, echoless, enduring,
   even-tenored, firm, fixed, frozen, halcyon, hush as death, hushed,
   idle, immobile, immutable, impassive, inactive, inaudible, inert,
   intact, inviolate, isolated, laissez-aller, laissez-faire, lasting,
   lurking, meditative, moldering, motionless, mousy, neuter, neutral,
   noiseless, pacific, paralytic, paralyzed, passive, peaceable,
   peaceful, permanent, perpetual, persistent, placid, potential,
   procrastinating, quiet, quietist, quietistic, remaining, reposeful,
   reposing, restful, resting, rigid, secluded, sedentary,
   sequestered, sequestrated, sheltered, silent, smooth, solid,
   soundless, stable, stagnant, stagnating, standpat, static,
   stationary, staying, steadfast, still, still as death, stillish,
   stilly, stoic, stolid, subaudible, subsiding, sustained, torpid,
   tranquil, unactive, unagitated, unaltered, unarticulated,
   unchangeable, unchanged, unchanging, unchecked, undestroyed,
   undisturbed, unfading, unfailing, unhearable, unmoved, unperturbed,
   unpronounced, unruffled, unshifting, unsounded, unstirring,
   untroubled, unuttered, unvaried, unvarying, unvocalized, unvoiced,
   vegetable, vegetative, waning, whist