Marika,
Here is what GuruNet has to say. I believe I posted about
GuruNet in Announcements. Also, this Board does have a
Q&A about Words section. Not to worry--it takes a while to
find your way around, esp. for someone living three
different roles!


watershed

Dictionary Encyclopedia Thesaurus Science Translation Internet Keywords Web Search Books What's New! wa·ter·shed (wô'tər-shĕd', wŏt'ər-)
n.
A ridge of high land dividing two areas that are drained by different river systems.
Also called: water parting
The region draining into a river, river system, or other body of water.
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).

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The American Heritage® Dictionary of the English Language, Third Edition Copyright © 1992, 1996 by Houghton Mifflin Company. All rights reserved.
watershed, elevation or divide separating the catchment area, or drainage basin, of one river system from another. The Rocky Mts. and the Andes form a watershed between westward-flowing and eastward-flowing streams. The term is also often synonymous with drainage basin.