define seaweed
Wiktionary(0.00 / 0 votes)Rate this definition: Any of numerous marine plants and algae, such as a kelp. Webster Dictionary(0.00 / 0 votes)Rate this definition: Freebase(0.00 / 0 votes)Rate this definition: Seaweed is a loose colloquial term encompassing macroscopic, multicellular, benthic marine algae. The term includes some members of the red, brown and green algae. Seaweeds can also be classified by use.