1. A submerged aquatic plant with small leaves native to Asia, often considered an invasive species in freshwater ecosystems.
Usage: Also called waterthyme; Scientific name: Hydrilla verticillata; Commonly used in aquarium contexts and as a biological term

Examples

• Hydrilla has spread rapidly through lakes and rivers in the southern United States.
• The aquarium keeper added hydrilla to provide oxygen and shelter for the fish.
• Environmental agencies work to control hydrilla infestations because they clog waterways.
• Hydrilla's dense growth can outcompete native aquatic plants.
• The pond became choked with hydrilla within a single growing season.