The Collaborative International Dictionary of English v.0.48:

Teratology \Ter`a*tol"o*gy\, n. [Gr. ?, ?, a wonder, monster +
   -logy: cf. Gr. ? a telling of wonders, and F.
   t['e]ratologie.]
   1. That branch of biological science which treats of
      monstrosities, malformations, or deviations from the
      normal type of structure, either in plants or animals.
      [1913 Webster]

   2. Affectation of sublimity; bombast. [Obs.] --Bailey.
      [1913 Webster]

WordNet (r) 3.0 (2006):

teratology
    n 1: the branch of biology concerned with the development of
         malformations or serious deviations from the normal type of
         organism