Definition of "pondweed"

Any of several plants that grow in ponds or similar aquatic conditions:

1. (most commonly) Potamogeton, a diverse and worldwide genus  examples

2. Elodea, found in North America  examples

3. Azolla, of cosmopolitan distribution  quotations  examples

   Quotations

   • If you have ever had a pond you will know Azolla, a.k.a. pondweed, duckweed fern or fairy moss.

     2018, Tim Flannery, Europe: A Natural History, page 76

4. Aponogeton, in Africa, Asia and Australasia  examples

5. opposite-leaved pondweed, Groenlandia densa, only plant of its genus, found chiefly in the Mediterranean region.  examples

Charales, an order of green algae  examples