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[tahl-veg, -veyk] /ˈtɑl vɛg, -veɪk/
a line, as drawn on a map, connecting the lowest points of a valley.
Chiefly International Law. the middle of the main navigable channel of a waterway that serves as a boundary line between states.
Origin of thalweg
1860-65; < German, equivalent to Thal, now obsolete spelling of Tal valley (cognate with dale) + Weg way1 Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for thalweg
Historical Examples
  • The thalweg has been frequently confirmed as the accepted boundary where no conventions to the contrary existed.

    International Law

    George Grafton Wilson and George Fox Tucker
British Dictionary definitions for thalweg


noun (geography, rare)
the longitudinal outline of a riverbed from source to mouth
the line of steepest descent from any point on the land surface
Word Origin
C19: from German, from Thal valley + Weg way, path
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for thalweg

1831, from German Thalweg "path along the bottom of a valley," from thal (see dale) + weg (see way).

Online Etymology Dictionary, © 2010 Douglas Harper
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thalweg in Science
  1. The line defining the lowest points along the length of a river bed or valley, whether underwater or not.

  2. A subterranean stream following a course similar to that of an overlying surficial stream.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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