Watershed
Pronunciation : Wa"ter*shed`
Part of Speech : n.
Etymology : [Cf. G. wasserscheide; wasser water + scheide a place where two things separate, fr. scheiden to separate.]
Definition : 1. The whole region or extent of country which contributes to the supply of a river or lake.
2. The line of division between two adjacent rivers or lakes with respect to the flow of water by natural channels into them; the natural boundary of a basin.
Source : Webster's Unabridged Dictionary, 1913