The American Heritage® Dictionary of the English Language, 4th Edition
n. Any of several submerged plants of the genus Ceratophyllum, forming branched masses in quiet water and having finely dissected, whorled leaves and minute unisexual flowers.
n. A bryophyte with a leafless thallus characterized by a dominant gametophyte stage of the life cycle and a sporophyte stage shaped like a horn.
the GNU version of the Collaborative International Dictionary of English
n. An aquatic plant (Ceratophyllum), with finely divided leaves.
The Century Dictionary and Cyclopedia
n. An aquatic plant of the genus Ceratophyllum, the single species of which, C. demersum, is common in ponds and slow streams in most parts of the world. See cut under Ceratophyllaceæ.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. liverworts with slender hornlike capsules
n. any aquatic plant of the genus Ceratophyllum; forms submerged masses in ponds and slow-flowing streams
Word Usage
"Even so, I bought the hornwort and three white clouds and went home."