sargassum

noun

sar·​gas·​sum sär-ˈga-səm 

: any of a genus (Sargassum) of brown algae that have a branching thallus with lateral outgrowths differentiated as leafy segments, air bladders, or spore-bearing structures : gulfweed

Examples of sargassum in a Sentence

Recent Examples on the Web

Large sargassum deposits can block sunlight needed by coral reefs and sea grass meadows, while organisms within the wash die or are scavenged by birds. —Sophie Clark, MSNBC Newsweek, 6 June 2025

The University of South Florida’s Optical Oceanography Lab tracks the growth of this type of seaweed, called sargassum, closely. —Alix Martichoux, The Hill, 4 June 2025

Brown seaweed has already begun to wash up on Miami's beaches, but researchers predict a record amount of the stinky sargassum could still be on its way. —Martin Vassolo, Axios, 6 May 2025

Found mostly from the Carolinas to Florida, throughout the Caribbean, and the Southern Pacific, sargassum mats can be miles long. —Joe Cermele, Outdoor Life, 19 Sep. 2024

Word History

Etymology

borrowed from New Latin, borrowed from Portuguese sargaço sargasso

First Known Use

circa 1890, in the meaning defined above

Kids Definition

sargassum

noun

sar·​gas·​sum sär-ˈgas-əm 

: any of a genus of brown algae that have a leafy branching body and air bladders and that often grow in free-floating masses in the ocean