- (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.
- (hydrology) The topographical boundary dividing two adjacent catchment basins, such as a ridge or a crest.
- (Canada, Britain) 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)
- A critical point marking a change in course or development.