The Collaborative International Dictionary of English v.0.48:

Antefix \An"te*fix`\, n.; pl. E. Antefixes; L. Antefixa. [L.
   ante + fixus fixed.] (Arch.)
   (a) An ornament fixed upon a frieze.
   (b) An ornament at the eaves, concealing the ends of the
       joint tiles of the roof.
   (c) An ornament of the cymatium of a classic cornice,
       sometimes pierced for the escape of water.
       [1913 Webster]

WordNet (r) 3.0 (2006):

antefix
    n 1: carved ornament at the eaves of a tile roof concealing the
         joints between tiles