The Collaborative International Dictionary of English v.0.48:

Astragal \As"tra*gal\, n. [L. astragalus, Gr. ? the ankle bone,
   a molding in the capital of the Ionic column.]
   1. (Arch.) A convex molding of rounded surface, generally
      from half to three quarters of a circle.
      [1913 Webster]

   2. (Gun.) A round molding encircling a cannon near the mouth.
      [1913 Webster]

WordNet (r) 3.0 (2006):

astragal
    n 1: the bone in the ankle that articulates with the leg bones
         to form the ankle joint [syn: anklebone, astragal,
         astragalus, talus]
    2: a beaded molding for edging or decorating furniture [syn:
       beading, bead, beadwork, astragal]