The Collaborative International Dictionary of English v.0.48:

Poem \Po"em\, n. [L. po["e]ma, Gr. ?, fr. ? to make, to compose,
   to write, especially in verse: cf. F. po["e]me.]
   1. A metrical composition; a composition in verse written in
      certain measures, whether in blank verse or in rhyme, and
      characterized by imagination and poetic diction; --
      contradistinguished from prose; as, the poems of Homer or
      of Milton.
      [1913 Webster]

   2. A composition, not in verse, of which the language is
      highly imaginative or impassioned; as, a prose poem; the
      poems of Ossian.
      [1913 Webster]

WordNet (r) 3.0 (2006):

poem
    n 1: a composition written in metrical feet forming rhythmical
         lines [syn: poem, verse form]