The Collaborative International Dictionary of English v.0.48:

Metamere \Met"a*mere\, n. [Pref. meta- + -mere.] (Biol.)
   One of successive or homodynamous parts in animals and
   plants; one of a series of similar parts that follow one
   another in a vertebrate or articulate animal, as in an
   earthworm; a segment; a somite. See Illust. of Loeven's
   larva.
   [1913 Webster]

WordNet (r) 3.0 (2006):

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