Source : Webster's Revised Unabridged Dictionary (1913)

Water parting \Water parting\ (Phys. Geog.)
   A summit from the opposite sides of which rain waters flow to
   different streams; a line separating the drainage districts
   of two streams or coasts; a divide.

Source : WordNet®

water parting
     n : a ridge of land that separates two adjacent river systems
         [syn: {watershed}, {divide}]