The Collaborative International Dictionary of English v.0.48:

Gland \Gland\, n. [F. glande, L. glans, glandis, acorn; akin to
   Gr. ? for ?, and ? to cast, throw, the acorn being the
   dropped fruit. Cf. Parable, n.]
   [1913 Webster]
   1. (Anat.)
      (a) An organ for secreting something to be used in, or
          eliminated from, the body; as, the sebaceous glands of
          the skin; the salivary glands of the mouth.
      (b) An organ or part which resembles a secreting, or true,
          gland, as the ductless, lymphatic, pineal, and
          pituitary glands, the functions of which are very
          imperfectly known.
          [1913 Webster]

   Note: The true secreting glands are, in principle, narrow
         pouches of the mucous membranes, or of the integument,
         lined with a continuation of the epithelium, or of the
         epidermis, the cells of which produce the secretion
         from the blood. In the larger glands, the pouches are
         tubular, greatly elongated, and coiled, as in the sweat
         glands, or subdivided and branched, making compound and
         racemose glands, such as the pancreas.
         [1913 Webster]

   2. (Bot.)
      (a) A special organ of plants, usually minute and
          globular, which often secretes some kind of resinous,
          gummy, or aromatic product.
      (b) Any very small prominence.
          [1913 Webster]

   3. (Steam Mach.) The movable part of a stuffing box by which
      the packing is compressed; -- sometimes called a
      follower. See Illust. of Stuffing box, under
      Stuffing.
      [1913 Webster]

   4. (Mach.) The crosspiece of a bayonet clutch.
      [1913 Webster]

WordNet (r) 3.0 (2006):

gland
    n 1: any of various organs that synthesize substances needed by
         the body and release it through ducts or directly into the
         bloodstream [syn: gland, secretory organ, secretor,
         secreter]

Moby Thesaurus II by Grady Ward, 1.0:

38 Moby Thesaurus words for "gland":
   acromegaly, adrenal, breast, choriocarcinoma, cretinism, diabetes,
   diabetes insipidus, diabetes mellitus, dwarfism, gasket, giantism,
   hyperglycemia, hyperparathyroidism, hypo-ovarianism,
   hypothyroidism, liver, mamma, mammary gland, ovary, packing,
   padding, pancreas, panhypopituitarism, pheochromocytoma,
   pineal body, prostate, prostate gland, sexual precocity, spermary,
   stopping, stuffing, tampon, testicle, thyroid, thyroid gland,
   thyrotoxicosis, toxic goiter, wadding