1. [noun] (hydrology) The topographical boundary dividing two adjacent catchment basins, such as a ridge or a crest.
2. [noun] (US) A region of land within which water flows down into a specified body, such as a river, lake, sea, or ocean; a drainage basin.
3. [noun] A critical point marking a change in course or development.
4. [noun] (Canada) (British) The time after which material of more adult nature (violence, swear words, sex) may be broadcast on television or radio, either one laid down or one contrived (e.g. when children are not watching)
5. [noun] A ridge of land that separates two adjacent river systems.
6. [noun] The entire geographical area drained by a river and its tributaries; an area characterized by all runoff being conveyed to the same outlet; 'flood control in the Missouri basin'.
7. [noun] 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'.
