watershed

American  

[waw-ter-shed, wot-er-] / ˈwɔ tərˌʃɛd, ˈwɒt ər- /

noun

1. Chiefly British. the ridge or crest line dividing two drainage areas; water parting; divide.

2. the region or area drained by a river, stream, etc.; drainage area.

3. Architecture. wash.

4. an important point of division or transition between two phases, conditions, etc..

   The treaty to ban war in space may prove to be one of history's great watersheds.

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adjective

1. constituting a watershed.

   a watershed area; a watershed case.

watershed British  

/ ˈwɔːtəˌʃɛd /

noun

1. the dividing line between two adjacent river systems, such as a ridge

2. an important period or factor that serves as a dividing line

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watershed Scientific  

/ wô′tər-shĕd′ /

1. A continuous ridge of high ground forming a divide between two different drainage basins or river systems.

2. The region enclosed by such a divide and draining into a river, river system, or other body of water.

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watershed Cultural  

1. 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.

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Discover More

By extension, a “watershed” is a critical point that serves as a dividing line: “The parties reached a watershed in the contract negotiations.”

Etymology

Origin of watershed

First recorded in 1795–1805; water + shed ²

Explanation

A watershed is a turning point, or historic moment. The day you got your braces off might have been a watershed moment in your life. Watershed is a geographical term, originally. The area that drains into a single river is the watershed for that river. Watershed can also mean a ridge, like that formed by a chain of mountains, which sends water to two different rivers on either side. It's from this meaning that watershed came to mean a turning point or dividing line in social life.

Example Sentences

But I would always hope for us to have some crazy watershed moment in addition to this natural grinding momentum we’ve built.

From Los Angeles Times • Apr. 30, 2026

The gains came on the heels of a watershed year for quantum investment.

From Barron's • Apr. 27, 2026

The independent charity and healthcare think tank said this drop posed a significant economic cost and should be a "watershed moment".

From BBC • Apr. 27, 2026

Anne Quinn Young, the chief mission officer of the Multiple Myeloma Research Foundation, the country’s largest funder of myeloma research, calls the new IMS definition of the term cure “a watershed moment.”

From Slate • Mar. 29, 2026

The Chicago meeting was the watershed moment in the atomic bomb project.

From "Big Science" by Michael Hiltzik

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