The Collaborative International Dictionary of English v.0.48:

Ganglion \Gan"gli*on\, n.; pl. L. Ganglia, E. Ganglions. [L.
   ganglion a sort of swelling or excrescence, a tumor under the
   skin, Gr. ?: cf. F. ganglion.]
   1. (Anat.)
      (a) A mass or knot of nervous matter, including nerve
          cells, usually forming an enlargement in the course of
          a nerve.
      (b) A node, or gland in the lymphatic system; as, a
          lymphatic ganglion.
          [1913 Webster]

   2. (Med.) A globular, hard, indolent tumor, situated
      somewhere on a tendon, and commonly formed by the effusion
      of a viscid fluid into it; -- called also weeping sinew.
      [1913 Webster]

   Ganglion cell, a nerve cell. See Illust. under Bipolar.
      [1913 Webster]