watershed: noun
1 a: a dividing ridge between drainage areas
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
3 BRITISH: the time of day after which television programs not appropriate for children may be broadcast
4 medical: an area of tissue that is located at the periphery of two separate arterial systems, is dependent for blood supply, and may be poorly perfused and vulnerable to ischemia (usually used before another noun)
