'Headwater' definitions:

Definition of 'headwater'

From: WordNet
noun
The source of a river; "the headwaters of the Nile"

Definition of 'Headwater'

From: GCIDE
  • Headwater \Head"wa`ter\ (-w[=a]`), n. The source and upper part of a stream; -- commonly used in the plural; as, the headwaters of the Missouri. [Webster 1913 Suppl.]