Source : Webster's Revised Unabridged Dictionary (1913)

Astragalus \As*trag"a*lus\, n. [L. See {Astragal}.]
   1. (Anat.) The ankle bone, or hock bone; the bone of the
      tarsus which articulates with the tibia at the ankle.

   2. (Bot.) A genus of papilionaceous plants, of the tribe
      {Galege[ae]}, containing numerous species, two of which
      are called, in English, {milk vetch} and {licorice vetch}.
      {Gum tragacanth} is obtained from different oriental
      species, particularly the {A. gummifer} and {A. verus}.

   3. (Arch.) See {Astragal}, 1.

Source : WordNet®

Astragalus
     n 1: large genus of annual or perennial herbs or shrubs of north
          temperate regions; largest genus in the family
          Leguminosae [syn: {genus Astragalus}]
     2: the bone in the ankle that articulates with the leg bones to
        form the ankle joint [syn: {anklebone}, {astragal}, {talus}]