Main Entry: wa·ter·shed
Function: noun
Date: 1803
1 a: divide 2a b: a region or area bounded peripherally by a divide and draining ultimately to a particular watercourse or body of water
2: a crucial dividing point, line, or factor : turning point
or
wa·ter·shed
–noun 1. Chiefly British. the ridge or crest line dividing two drainage areas; water parting; divide.
2. the region or area drained by a river, stream, etc.; drainage area.
3. Architecture. wash (def. 44).
4. an important point of division or transition between two phases, conditions, etc.: The treaty to ban war in space may prove to be one of history's great watersheds.
–adjective 5. constituting a watershed: a watershed area; a watershed case.