hīˈdrilə noun
( -s )
Etymology: New Latin, probably from Latin Hydra mythical water serpent killed by Hercules (from Greek) + New Latin -illa -illa — more at hydra
: a freshwater aquatic plant ( Hydrilla verticillata ) of the family Hydrocharitaceae native to Asia that resembles elodea and has small narrow serrated leaves with spines on the midrib undersurface that grow in whorls of three to eight around stems which become heavily branched near the water surface and that was introduced into Florida around 1960 for aquarium use and has since become a serious invasive weed