thalweg
n.— «Then, former president, Saddam Hussein, disputed the Algiers Accord, which ruled the maritime border between the two countries ran along the median line of the deep-water channel, also known as the thalweg.» —“AM: Diplomatic scandal as Iran intercepts British naval vessels” by Kirsten Aiken Austral. Broadcasting Corp. (Ultimo, New South Wales) June 22, 2004. (source: Double-Tongued Dictionary)
Further reading
Twice a day the River Thames recedes, revealing a muddy shoreline. Hobbyists known as mudlarks stroll the surface searching for objects that have found their way into the river over the centuries, everything from ancient Roman jewelry to modern...
What if, instead of being an inanimate object, a dictionary were alive? That’s the idea behind a lavishly illustrated new children’s book called The Dictionary Story (Bookshop|Amazon) by Oliver Jeffers and Sam Winston. This is part of a...