The Collaborative International Dictionary of English v.0.48:

Somite \So"mite\ (s[=o]"m[imac]t), n. [Gr. sw^ma body.] (Anat. &
   Zool.)
   One of the actual or ideal serial segments of which an
   animal, esp. an articulate or vertebrate, is composed;
   somatome; metamere. -- So*mit`ic, a.
   [1913 Webster]

WordNet (r) 3.0 (2006):

somite
    n 1: one of a series of similar body segments into which some
         animals are divided longitudinally [syn: metamere,
         somite]