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]

Moby Thesaurus II by Grady Ward, 1.0:

129 Moby Thesaurus words for "poem":
   English sonnet, Horatian ode, Italian sonnet, Petrarchan sonnet,
   Pindaric ode, Sapphic ode, Shakespearean sonnet, alba, anacreontic,
   article, autograph, balada, ballad, ballade, brainchild, bucolic,
   canso, chanson, clerihew, composition, computer printout, copy,
   dirge, dithyramb, ditty, document, draft, eclogue, edited version,
   elegy, engrossment, epic, epigram, epithalamium, epode, epopee,
   epopoeia, epos, essay, eyeful, fair copy, fiction, final draft,
   finished version, first draft, flimsy, georgic, ghazel, haiku,
   holograph, idyll, jingle, letter, limerick, literae scriptae,
   literary artefact, literary production, literature, lucubration,
   lyric, madrigal, manuscript, matter, monody, narrative poem,
   nonfiction, nursery rhyme, ode, opus, original, palinode, paper,
   parchment, pastoral, pastoral elegy, pastorela, pastourelle,
   penscript, picture, piece, piece of writing, play, poesy, poetry,
   printed matter, printout, production, prothalamium, reading matter,
   recension, rhapsody, rhyme, rondeau, rondel, roundel, roundelay,
   rune, satire, screed, scrip, script, scrive, scroll, second draft,
   sestina, sloka, song, sonnet, sonnet sequence, tanka, tenso,
   tenzone, the written word, thing of beauty, threnody, transcript,
   transcription, triolet, troubadour poem, typescript, verse,
   verselet, versicle, version, villanelle, virelay, vision, work,
   writing



V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

POEM
       Portable Object-orientated Entity Manager (SGML)