definition of
watershed

[1] #1 watershed n. [water parting, divide] a ridge of land that separates two adjacent river systems. wn

[2] #2 watershed n. [river basin, basin, drainage basin, catchment area, catchment basin, drainage area] 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". wn

[3] #3 watershed n. [landmark, turning point] 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". wn