Source : Webster's Revised Unabridged Dictionary (1913)

Calamus \Cal"a*mus\, n.; pl. {Calami}. [L., a reed. See {Halm}.]
   1. (Bot.) The indian cane, a plant of the Palm family. It
      furnishes the common rattan. See {Rattan}, and {Dragon's
      blood}.

   2. (Bot.) A species of {Acorus} ({A. calamus}), commonly
      called {calamus}, or {sweet flag}. The root has a pungent,
      aromatic taste, and is used in medicine as a stomachic;
      the leaves have an aromatic odor, and were formerly used
      instead of rushes to strew on floors.

   3. (Zo["o]l.) The horny basal portion of a feather; the
      barrel or quill.

Source : WordNet®

calamus
     n 1: any tropical Asian palm of the genus Calamus; light tough
          stems are a source of rattan canes
     2: the aromatic root of the sweet flag used medicinally
     3: perennial marsh plant having swordlike leaves and aromatic
        roots [syn: {sweet flag}, {sweet calamus}, {myrtle flag},
        {flagroot}, {Acorus calamus}]
     4: a genus of Sparidae [syn: {genus Calamus}]
     5: the hollow shaft of a feather [syn: {quill}, {shaft}]
     [also: {calami} (pl)]