The Collaborative International Dictionary of English v.0.48:

Choragus \Cho*ra"gus\, n.; pl. Choragi. [L., fr. Gr. ?, ?; ?
   chorus + ? to lead.] (Gr. Antiq.)
   A chorus leader; esp. one who provided at his own expense and
   under his own supervision one of the choruses for the musical
   contents at Athens.
   [1913 Webster]

WordNet (r) 3.0 (2006):

choragus
    n 1: (ancient Greece) leader of a group or festival; leader of a
         chorus