名詞 thalweg:

1. the middle of the chief navigable channel of a waterway that forms the boundary line between states
2. a line following the lowest points of a valley

thal.weg

n.Geology （名詞）【地質(zhì)學(xué)】
The line defining the lowest points along the length of a river bed or valley.
河流谷底線：延著整條河床或河谷長度，用來界定最低點的線
A subterranean stream.
地下溪流

來源：
German
German
Tal, Thal [valley] from Middle High German tal from Old High German
Tal, Thal [valley] from Middle High German tal from Old High German
Weg [way] from Middle High German wec, weg from Old High German weg * see wegh-
Weg [way] from Middle High German wec, weg from Old High German weg *參見 wegh-