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| a screen or mat covered with a dark material for shielding a camera lens from excess light or glare. |
| a children's mummer's parade, as on the Fourth of July, with prizes for the best costumes. |
Based on the Random House Dictionary, © Random House, Inc. 2012.
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- The vaccinal eradication of smallpox was a watershed achievement.
- Human population density in the watershed is high, yet elephant and buffalo populations have not dropped.
- Population pressure is becoming more intense, forcing farmers onto steeper lands in the upper watershed forests of this ecoregion.
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watershed wa·ter·shed (wô'tər-shěd')
n.
A ridge between two areas that directs drainage to either side.
The area of marginal blood flow at the extreme periphery of a vascular bed.
Ridges of the lumbar vetebrae and the pelvic brim formed in the abdominal cavity, which determine the direction in which a free effusion will gravitate when the body is supine.
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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watershed  (wô'tər-shěd') Pronunciation Key
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Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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watershed definition
A ridge of high land dividing two areas that are drained by different river systems. On one side of a watershed, rivers and streams flow in one direction; on the other side they flow in another direction. Also, the area drained by a water system.
Note: By extension, a “watershed” is a critical point that serves as a dividing line: “The parties reached a watershed in the contract negotiations.”
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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watershed
area from which all precipitation flows to a single stream or set of streams. For example, the total area drained by the Mississippi River constitutes its drainage basin, whereas that part of the Mississippi River drained by the Ohio River is the Ohio's drainage basin. The boundary between drainage basins is a drainage divide: all the precipitation on opposite sides of a drainage divide will flow into different drainage basins.
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