The Collaborative International Dictionary of English v.0.48:

Armilla \Ar*mil"la\, n.; pl. E. Armillas, L. Armill[ae].
   [L., a bracelet.]
   1. An armil.
      [1913 Webster]

   2. (Zool.) A ring of hair or feathers on the legs.
      [1913 Webster]

WordNet (r) 3.0 (2006):

armilla
    n 1: a celestial globe consisting of metal hoops; used by early
         astronomers to determine the positions of stars [syn:
         armillary sphere, armilla]
    2: (archeology) a bracelet worn around the wrist or arm