Wordnet 3.0
NOUN (1)
1.
any of various submerged aquatic algae of the genus Chara having nodes with whorled filamentlike branches;
usually encrusted with calcium carbonate deposits;
The Collaborative International Dictionary of English v.0.48:
Stonewort \Stone"wort`\, n. (Bot.)
Any plant of the genus Chara; -- so called because they are
often incrusted with carbonate of lime. See Chara.
[1913 Webster]
WordNet (r) 3.0 (2006):
stonewort
n 1: any of various submerged aquatic algae of the genus Chara
having nodes with whorled filamentlike branches; usually
encrusted with calcium carbonate deposits