watershed

Plural: watersheds

Noun

• a ridge of land that separates two adjacent river systems
• the entire geographical area drained by a river and its tributaries; an area characterized by all runoff being conveyed to the same outlet
• an event marking a unique or important historical change of course or one on which important developments depend
  • "the agreement was a watershed in the history of both nations"
• The topographical boundary dividing two adjacent catchment basins, such as a ridge or a crest.
• A region of land within which water flows down into a specified body, such as a river, lake, sea, or ocean; a drainage basin.
• A critical point marking a change in course or development.
• The time during the day which material of a more adult nature (e.g., violence, swear words, or sex) may be broadcast on television or radio, either one permitted by law or one contrived from convention (e.g. when children are not watching).

Adj

• Serving to mark a significant development, change in direction, etc.

Synonyms

basin, catchment area, catchment basin, divide, drainage area, drainage basin, landmark, river basin, turning point, water parting, catchment, climacteric, crossroads, drainage divide, momentous, safe harbor, water basin, water divide