wa·ter·shed (wôtər-shĕd′, wŏtər-)
1. The entire region draining into a river, river system, or other body of water: a list of reptiles found in the watershed. Also called basin, drainage basin.
2. A ridge of high land dividing two areas that are drained by different river systems. Also called divide, water parting.
3. A critical point that marks a division or a change of course; a turning point: "a watershed in modern American history, a time that ... forever changed American social attitudes" (Robert Reinhold).
[Probably translation of German Wasserscheide, water parting, border between watersheds : Wasser, water + Scheide, divide, parting.]
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