Source : Webster's Revised Unabridged Dictionary (1913)

Toponym \Top"o*nym\, n.
   A name of a place; more broadly, a name, as in the binomial
   name of a plant, based on, or derived from, a place name, or
   based on the location of the thing named.

Source : WordNet®

toponym
     n : the name by which a geographical place is known [syn: {place
         name}]