The Collaborative International Dictionary of English v.0.48:

Cinnamon \Cin"na*mon\, n. [Heb. qinn[=a]m[=o]n; cf. Gr. ?, ?,
   cinnamomum, cinnamon. The Heb. word itself seems to have been
   borrowed from some other language; cf. Malay k[=a]j[=u]
   m[=a]nis sweet wood.]
   (a) The inner bark of the shoots of Cinnamomum Zeylanicum,
       a tree growing in Ceylon. It is aromatic, of a moderately
       pungent taste, and is one of the best cordial,
       carminative, and restorative spices.
   (b) Cassia.
       [1913 Webster]

   Cinnamon stone (Min.), a variety of garnet, of a cinnamon
      or hyacinth red color, sometimes used in jewelry.

   Oil of cinnamon, a colorless aromatic oil obtained from
      cinnamon and cassia, and consisting essentially of
      cinnamic aldehyde, C6H5.C2H2.CHO.

   Wild cinnamon. See Canella.
      [1913 Webster]

WordNet (r) 3.0 (2006):

cinnamon
    n 1: aromatic bark used as a spice [syn: cinnamon, cinnamon
         bark]
    2: tropical Asian tree with aromatic yellowish-brown bark;
       source of the spice cinnamon [syn: cinnamon, Ceylon
       cinnamon, Ceylon cinnamon tree, Cinnamomum zeylanicum]
    3: spice from the dried aromatic bark of the Ceylon cinnamon
       tree; used as rolled strips or ground

Easton's 1897 Bible Dictionary:

Cinnamon
   Heb. kinamon, the Cinnamomum zeylanicum of botanists, a tree of
   the Laurel family, which grows only in India on the Malabar
   coast, in Ceylon, and China. There is no trace of it in Egypt,
   and it was unknown in Syria. The inner rind when dried and
   rolled into cylinders forms the cinnamon of commerce. The fruit
   and coarser pieces of bark when boiled yield a fragrant oil. It
   was one of the principal ingredients in the holy anointing oil
   (Ex. 30:23). It is mentioned elsewhere only in Prov. 7:17; Cant.
   4:14; Rev. 18:13. The mention of it indicates a very early and
   extensive commerce carried on between Palestine and the East.