sea·​weed ˈsē-ˌwēd How to pronounce seaweed (audio)
plural seaweeds : any of various aquatic and chiefly marine brown, red, or green algae (such as rockweed, gulfweed, and kelp) that often grow in masses, typically have leaflike blades (see blade entry 1 sense 2e), are usually anchored to a solid substrate (such as a rock) by holdfasts (see holdfast sense 2a), and include some (such as dulse, laver, and sea lettuce) that are used as food
… many seaweeds have floats called pneumatocysts, filled with oxygen or carbon dioxide.Michael Le Page
The word seaweed is broad and refers generally to marine macroalgae, which are algae living in salt or brackish water and visible to the eye.Elyse Inamine
: a mass or growth of seaweeds
… soft crabs were easily visible in the seaweed, because the water was crystal clear then.Keith Walters
: harvested seaweed or seaweed parts used especially as food, fertilizer, and in cosmetics
… sushi rolls wrapped in thin sheets of dried seaweedJane Snow

Examples of seaweed in a Sentence

Recent Examples on the Web And there’s plenty of seaweed to experiment with, Paslier points out. Stephen Armstrong, WIRED, 15 Feb. 2024 Spend the morning snorkeling with the knowledgeable chef and learn about the 11 varieties of seaweed surrounding the island (like grass kelp, bladderwrack, and sugar-kelp—used in the seaweed creams in the bathroom and also served at dinner). Michelle Tchea, Robb Report, 30 Jan. 2024 At one farm, a blend of seaweed is mixed into cow feed to reduce emissions from belches. Laura Reiley, Washington Post, 22 Jan. 2024 Capturing natural seaweed As some people contemplate growing enormous amounts of seaweed, others are already dealing with huge influxes. Saima May Sidik, Smithsonian Magazine, 22 Jan. 2024 The rounds of seaweed are crisp and curved, cradling a smear of mashed avocado and a heap of caviar. Jenn Harris, Los Angeles Times, 17 Jan. 2024 Turning seaweed into plant food is one of six proposals that Miami-Dade is considering as part of a county effort to find new ways to deal with a seaweed surge that scientists expect climate change will only make worse. Ashley Miznazi, Sun Sentinel, 3 Jan. 2024 The agency has now selected six finalists to come up with environmentally friendly ways to get rid of all the seaweed that annually piles up on South Florida’s shores. Ashley Miznazi, Miami Herald, 3 Jan. 2024 Scientists have used teeth to determine that early Europeans snacked on seaweed, that male woolly mammoths went through musth similar to today’s elephants and that early humans might have cooked their fish before eating it some 780,000 years ago. Sarah Kuta, Smithsonian Magazine, 8 Jan. 2024 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'seaweed.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

First Known Use

1577, in the meaning defined at sense 1a

Time Traveler
The first known use of seaweed was in 1577

Dictionary Entries Near seaweed

Cite this Entry

“Seaweed.” Dictionary, Merriam-Webster, Accessed 26 Feb. 2024.

Kids Definition


sea·​weed -ˌwēd How to pronounce seaweed (audio)
: a plant growing in the sea
especially : a marine alga (as a kelp)

More from Merriam-Webster on seaweed

Last Updated: - Updated example sentences
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!