The Collaborative International Dictionary of English v.0.48:

Biome \Bi"ome\ (b[imac]"[=o]m), n. [Gr. bi`os life.]
   1. (Ecology) a specific type of complex ecological community
      characterized by specific environmental conditions and a
      distinctive group of plants and animals, maintained in a
      relatively stable equilibrium, such as a rain forest
      biome or prairie biome.
      [PJC]

   2. a particular region which is a biome[1].
      [PJC]