watershed: Meaning and Definition of

wa•ter•shed

1. 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. wash (def. 48).
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.

1. constituting a watershed: a watershed area; a watershed case.