The Collaborative International Dictionary
Anacharis
Anacharis \An*ach"a*ris\, n. [NL., fr. Gr. ? up + ? grace.] (Bot.) A fresh-water weed of the frog's-bit family ( Hydrocharidace[ae]), native to America. Transferred to England it became an obstruction to navigation. Called also waterweed and water thyme.
Wiktionary
anacharis
n. (context obsolete English) A freshwater weed of the frog's-bit family ((taxlink Hydrocharidaceae family noshow=1)), native to America; the waterweed or water thyme.