1. a ridge of land that separates two adjacent river systems

Similar word(s): divide

Definition categories: location, line

2. the entire geographical area drained by a river and its tributaries; an area characterized by all runoff being conveyed to the same outlet

Similar word(s): basin

Definition categories: location

3. 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

Similar word(s): landmark

Definition categories: event, juncture, occasion