Thalweg

n. line drawn between the lowest points along a valley; line along the middle of a body water that separates between two countries

Thalweg (IPA: ; an English word compounded from the German elements Thal (since Duden's orthography reform of 1901 written Tal) meaning valley, and Weg, meaning way) is a term adopted into English usage for geography and geomorphology. It signifies the deepest continuous line along a valley or watercourse.
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Noun
1. the middle of the chief navigable channel of a waterway that forms the boundary line between states
(hypernym) boundary, edge, bound
2. a line following the lowest points of a valley
(hypernym) contour, contour line

n. thalweg, talweg, line drawn between the lowest points along a valley; line along the middle of a body water that separates between two countries

thalweg, line drawn between the lowest points along a valley; line along the middle of a body water that separates between two countries