has three Standard meanings. It is the dividing line between an area drained by a river running in one direction and one drained by another river running in an opposite direction.
The Continental Divide is a major watershed. A watershed is also an area drained by a river or river system: The watershed of the Connecticut River covers parts of four New England states. The figurative sense, a turning point, as in The decision marked a watershed in criminal legal theory, is sometimes overused, especially in journalese. A handful of purists still insist that only the first meaning is acceptable, but they’re out of touch: all three meanings are firmly established in American English.