The Collaborative International Dictionary of English v.0.48:

Subspecies \Sub*spe"cies\, n.
   A group somewhat lessdistinct than speciesusually are, but
   based on characters more important than those which
   characterize ordinary varieties; often, a geographical
   variety or race.
   [1913 Webster]

WordNet (r) 3.0 (2006):

subspecies
    n 1: (biology) a taxonomic group that is a division of a
         species; usually arises as a consequence of geographical
         isolation within a species [syn: subspecies, race]