Source : Webster's Revised Unabridged Dictionary (1913)

Polyhymnia \Pol`y*hym"ni*a\, n. [L., from Gr. ?; poly`s many + ?
   hymn.] (Anc. Myth.)
   The Muse of lyric poetry.

Source : WordNet®

Polyhymnia
     n : (Greek mythology) the Muse of singing and mime and sacred
         dance