The Collaborative International Dictionary of English v.0.48:

Versifier \Ver"si*fi`er\, n.
   1. One who versifies, or makes verses; as, not every
      versifier is a poet. --Dryden.
      [1913 Webster]

   2. One who converts into verse; one who expresses in verse
      the ideas of another written in prose; as, Dr. Watts was a
      versifier of the Psalms.
      [1913 Webster]

WordNet (r) 3.0 (2006):

versifier
    n 1: a writer who composes rhymes; a maker of poor verses
         (usually used as terms of contempt for minor or inferior
         poets) [syn: rhymer, rhymester, versifier,
         poetizer, poetiser]