| alligator weed n. An aquatic South American perennial plant (Alternanthera philoxeroides) having opposite, lance-shaped leaves and tight clusters of small whitish flowers. It is a mat-forming weed in warm, freshwater habitats, such as the southeast United States. |
| alligator weed | |
noun | |
| prolific South American aquatic weed having grasslike leaves and short spikes of white flowers; clogs waterways with dense floating masses |