watershed

UK: /ˈwɔːtə^rʃɛd/

US: /ˈwɔtɚˌʃɛd, ˈwɑtɚ-/

US: (wô′tər shed′, wot′ər-)

WordReference Random House Learner's Dictionary of American English © 2026

wa•ter•shed /ˈwɔtɚˌʃɛd, ˈwɑtɚ-/   n. [countable]

1. Geography a region or area drained by a river or stream.
2. Geography, British Terms a ridge or high area dividing two drainage areas.
3. an important point of division or change:
   a watershed in international relations.

WordReference Random House Unabridged Dictionary of American English © 2026

wa•ter•shed  (wô′tər shed′, wot′ər-), n. 

1. Geography, British Terms [Chiefly Brit.] the ridge or crest line dividing two drainage areas;
   water parting;
   divide.
2. Geography the region or area drained by a river, stream, etc.;
   drainage area.
3. Architecture wash (def. 48).
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.

adj. 

5. constituting a watershed:
   a watershed area; a watershed case.

• water + shed² 1795–1805

Collins Concise English Dictionary © HarperCollins Publishers::

watershed / 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