watershed

noun

wa·​ter·​shed ˈwȯ-tər-ˌshed 

ˈwä-

plural watersheds

1

a

: a dividing ridge between drainage areas : divide entry 2

The watershed of the Himalayas does not lie along the line of its highest peaks, as in most mountain ranges, but about a hundred miles farther north.

—Frits Staal

b

: a region or area bounded peripherally by a divide and draining ultimately to a particular watercourse or body of water

the Mississippi River watershed

2

: a crucial dividing point, line, or factor : turning point

This year marked a watershed for contemporary classical music in the city.

—The Chicago Tribune

The spring of 1949 was, in general, a watershed in Joe Liebling's life.

—Raymond Sokolov

The death of Ugandan teacher Gregory Byaruhanga at the hands of the Kenyan police has marked a watershed in the rising tension in the region and in the instability of the Kenyan regime.

—Victoria Brittain

—often used before another noun

a watershed moment

a watershed event

The watershed year for science fiction must be 1968, when Stanley Kubrick's 2001: A Space Odyssey appeared, not only dramatically expanding for this kind of motion picture the potentials of film technology, but making science fiction a vehicle for both poetic vision and metaphysical exploration.

—Ira Konigsberg

3

British : the time of day after which television programs not appropriate for children may be broadcast

the nine o'clock watershed

4

medical : an area of tissue (as of the brain or colon) that is located at the periphery of two separate arterial systems, is dependent on both for blood supply, and may be poorly perfused and vulnerable to ischemia

—usually used before another noun

Brain imaging of patients with vascular dementia typically show small strokes or poor blood supply deep in the brain, at the natural terminal (the so-called watershed area) of the blood vessel.

—Renee Meyer

… cell death caused by blocked blood flow in the brain's "watershed" region, where two arteries supply blood.

—Susan Scutti

see also watershed infarction

Did you know?

Watershed Has Geographic Origins

Opinion on the literal geographic meaning of watershed is divided. On one side of the debate are those who think the word can only refer to a ridge of land separating rivers and streams flowing in one direction from those flowing in the opposite direction. That's the term's original meaning, one probably borrowed in the translation of the German Wasserscheide. On the other side of the argument are those who think watershed can also apply to the area through which such divided water flows. The latter sense is now far more common in America, but most Americans have apparently decided to leave the quarrel to geologists and geographers while they use the term in its figurative sense, "turning point."        

Synonyms of watershed

• milestone
• climax
• landmark

Examples of watershed in a Sentence

The show will not air until after the nine o'clock watershed.

a watershed moment in her life came when she inherited a reasonable sum of money and was able to start her own coffee shop

Recent Examples on the Web

Their results suggest that early Mars was a patchwork of isolated watersheds, but that a small number of mega-basins acted as planetary conveyor belts, transporting nutrients and potential biosignatures across immense distances. —Sharmila Kuthunur, Space.com, 11 Dec. 2025

Environmental impact worries Spadaro, who has served as president of the Magothy River Association for more than 30 years, also expressed concerns about the potential environmental impact on the Magothy River and its surrounding watershed. —Caroline Foreback, CBS News, 8 Dec. 2025

Other initiatives include public art partnerships, climate and water-resilience workshops, the National Mayor’s Challenge for Water Conservation, and the Streams of Hope watershed program, which launched in 2022 and empowers middle-school students to adopt and study their local waterways. —Laylan Connelly, Oc Register, 5 Dec. 2025

This would be the first of three major dams that basically cut ocean-run fish from the entire watershed, said Jeff Miller, executive director of Alameda Creek Alliance. —Chase Hunter, Mercury News, 3 Dec. 2025

Word History

First Known Use

1839, in the meaning defined at sense 1a

Phrases Containing watershed

• watershed infarct
• watershed infarction
• watershed stroke

Rhymes for watershed

• abovesaid
• aforesaid
• arrowhead
• casinghead
• copperhead
• figurehead
• fountainhead
• gingerbread
• hammerhead
• infrared
• leatherhead
• letterhead

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Kids Definition

watershed

noun

wa·​ter·​shed ˈwȯt-ər-ˌshed 

ˈwät-

1

: a dividing ridge (as a mountain range) separating one drainage area from others

2

: the area that drains into a river or lake