continental divide

Short definition from Wiktionary

Noun

1. 1
   A line of elevated terrain that divides a watershed or a continent, so that water flowing on either side eventually travels to separate bodies of water.

Proper noun

1. 1
   An unincorporated community in McKinley County, New Mexico, United States.
2. 2
   A continental divide in the Americas to the west of which water drains into the Pacific Ocean, and to the east of which it flows variously into the Atlantic or Arctic Ocean.