Pondweed

n.
  1. Any aquatic plant of the genus Potamogeton, of which many species are found in ponds or slow-moving rivers.
    2. Choke pondweed ,
    an American water weed (Anarcharis Canadensis, syn. Elodea Canadensis.) See Anacharis.
    Horned pondweed ,
    the Zannichellia palustris, a slender, branching aquatic plant, having pointed nutlets.