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"