Definitions for "Alligator weed"
prolific South American aquatic weed having grasslike leaves and short spikes of white flowers; clogs waterways with dense floating masses
Alligator weed (Alternanthera philoxeroides) is an immersed aquatic plant. Alligator weed originated in South America, but it has spread to many parts of the world and is considered an invasive species in Australia, China, New Zealand, Thailand and the United States.