/ Dictionary / Index T thalweg: Meaning and Definition of Find definitions for: thal•weg Pronunciation: (täl'veg, -vāk), [key] — n. a line, as drawn on a map, connecting the lowest points of a valley. the middle of the main navigable channel of a waterway that serves as a boundary line between states. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: thalweg (Thesaurus) thallus Thamar Related Content Daily Word Quiz: immense Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language