- the ridge or crest line dividing two drainage areas; water parting; divide.
- the region or area drained by a river, stream, etc.; drainage area.
- wash (def. 45).
- 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.
- constituting a watershed: a watershed area; a watershed case.
- the dividing line between two adjacent river systems, such as a ridge
- an important period or factor that serves as a dividing line
