The Collaborative International Dictionary of English v.0.48:

Secretion \Se*cre"tion\, n. [L. secretio: cf. F.
   s['e]cr['e]tion.]
   1. The act of secreting or concealing; as, the secretion of
      dutiable goods.
      [1913 Webster]

   2. (Physiol.) The act of secreting; the process by which
      material is separated from the blood through the agency of
      the cells of the various glands and elaborated by the
      cells into new substances so as to form the various
      secretions, as the saliva, bile, and other digestive
      fluids. The process varies in the different glands, and
      hence are formed the various secretions.
      [1913 Webster]

   3. (Physiol.) Any substance or fluid secreted, or elaborated
      and emitted, as the gastric juice.
      [1913 Webster]

WordNet (r) 3.0 (2006):

secretion
    n 1: the organic process of synthesizing and releasing some
         substance [syn: secretion, secernment]
    2: a functionally specialized substance (especially one that is
       not a waste) released from a gland or cell

Moby Thesaurus II by Grady Ward, 1.0:

65 Moby Thesaurus words for "secretion":
   burial, burying, clouding, concealedness, concealment, covering,
   covering up, covertness, darkening, deception, discharge,
   discharging, drain, draining, dribbling, drip, dripping, drop,
   dropping, effusion, egestion, ejaculation, ejection, elimination,
   emanating, emanation, emission, escape, excreta, excreting,
   excretion, extravasate, extravasation, extrusion, exudation, flow,
   flux, generation, hiddenness, hiding, interment, invisibility,
   leak, leakage, leaking, masking, mystification, obscuration,
   obscurement, occultation, oozing, putting away, release, running,
   screening, secrecy, secreting, seepage, seeping, subterfuge,
   transudate, transudation, trickle, trickling,
   uncommunicativeness