The Collaborative International Dictionary of English v.0.48:

pectus \pec"tus\ (p[e^]k"t[u^]s), n.; pl. Pectora. [L., the
   breast.] (Zool.)
   The breast of a bird.
   [1913 Webster]

WordNet (r) 3.0 (2006):

pectus
    n 1: the part of the human torso between the neck and the
         diaphragm or the corresponding part in other vertebrates
         [syn: thorax, chest, pectus]