Any of numerous marine algae, such as a kelp, rockweed, or gulfweed.(noun)
Any of various marine plants.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "seaweed" in a sentence
"Indeed, he concludes that the term seaweed is inappropriate for the marine plants in question."
"The term seaweed carries the connotation that the plants under discussion are useless and worthless."
"The sun was setting between Eigg and Rum as we reached the deserted beach, only to find "VALHALLA DANCEHALL" spelt out in seaweed letters two foot high, which stumped even the locals."