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An aquatic plant (Hydrilla verticillata) native to Eurasia, Africa, and Australia, having whorled, lance-shaped leaves and small white flowers. It is considered a weed in North America, where it forms large dense mats in waterways.
[New Latin, genus name, diminutive of Latin hydra, hydra; see hydra.]
(Plants) any aquatic plant of the Eurasian genus Hydrilla, growing underwater and forming large masses: used as an oxygenator in aquaria and pools. It was introduced in the S US where it has become a serious problem, choking fish and hindering navigation
[C20: New Latin, probably from hydra]
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|Noun||1.||hydrilla - submersed plant with whorled lanceolate leaves and solitary axillary flowers; Old World plant naturalized in southern United States and clogging Florida's waterways|
genus Hydrilla - one species