bittern

plural bitterns

1. Several bird species in the Botaurinae subfamily of the heron family Ardeidae.

   It is a great rock or cliff on the loneliest part of the mountains, and […] is known by the name of the Garden Rock. Near the foot of it is a small lake, the haunt of the solitary bittern, with water-snakes basking in the sun on the leaves of the pond-lilies which lie on the surface.

   1819, Washington Irving, The Sketch Book, Rip Van Winkle

plural bitterns

1. countableuncountableThe liquor remaining after halite (common salt) has been harvested from saline water (brine).
2. countableuncountableThe saline substance added to soy milk to coagulate it as a primary step in the production of tofu.

   Now we add the bittern.

   2019, “The Secrets of Tofu across Japan”, in Seasoning the Seasons, NHK World-Japan

3. archaiccountableuncountableA very bitter compound of quassia, cocculus indicus, etc., used by fraudulent brewers in adulterating beer.

1. A town in the Shire of Mornington Peninsula, Victoria, Australia