'Thalweg' definitions:

Definition of 'thalweg'

From: WordNet
noun
The middle of the chief navigable channel of a waterway that forms the boundary line between states
noun
A line following the lowest points of a valley

Definition of 'Thalweg'

From: GCIDE
  • Thalweg \Thal"weg`\, n. [G., fr. thal valley + weg way. See Dale; Way.] (Physiography) (a) A line following the lowest part of a valley, whether under water or not. (b) The line of continuous maximum descent from any point on a land surface, or that cutting all contours and angles. [Webster 1913 Suppl.] Thammuz