The Collaborative International Dictionary of English v.0.48:

Monody \Mon"o*dy\, n.; pl. Monodies. [L. monodia, Gr. ?, fr. ?
   singing alone; mo`nos single + ? song: cf. F. monodie. See
   Ode.]
   A species of poem of a mournful character, in which a single
   mourner expresses lamentation; a song for one voice.
   [1913 Webster]

WordNet (r) 3.0 (2006):

monody
    n 1: music consisting of a single vocal part (usually with
         accompaniment) [syn: monophony, monophonic music,
         monody] [ant: concerted music, polyphonic music,
         polyphony]