'Stonewort' definitions:

Definition of 'stonewort'

(from WordNet)
noun
Any of various submerged aquatic algae of the genus Chara having nodes with whorled filamentlike branches; usually encrusted with calcium carbonate deposits

Definition of 'Stonewort'

From: GCIDE
  • 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]