Definitions

1. noun

a small aquatic plant, especially of the genus Ceratophyllum, having horn-like branching stems.

“The aquarium’s owner carefully planted the hornwort around the rocks to create a natural environment.”

2. noun

any of various other aquatic plants with horn-like structures, especially of the genus Zannichellia.

“The pond’s water plants included a variety of hornworts, adding to its ecosystem.”