seaweed

noun

sea·​weed ˈsē-ˌwēd 

1

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

2

: a mass or growth of seaweeds

… soft crabs were easily visible in the seaweed, because the water was crystal clear then.

—Keith Walters

3

: harvested seaweed or seaweed parts used especially as food, fertilizer, and in cosmetics

… sushi rolls wrapped in thin sheets of dried seaweed …

—Jane Snow

Examples of seaweed in a Sentence

Recent Examples on the Web

According to the documents filed with Port Angeles, Ebb’s technology includes comprehensive monitoring, modeling, and reporting systems to track the chemistry of the seawater and health of the marine ecosystem, from tiny plankton, seaweed, and salmon to the largest orcas and humpback whales. —IEEE Spectrum, 26 Mar. 2024

Types of sea algae, including seaweed and sea moss, are sometimes prone to accumulate heavy metals, according to the Ohio Department of Agriculture's Division of Food Safety. —Hannah Yasharoff, USA TODAY, 22 Mar. 2024

Recipes include citrus brandy, cold-brew coffee, yuzu, and shiso, or gin, seaweed, kaffir lime, and elderflower. —Tori Latham, Robb Report, 7 Mar. 2024

Anderson-Haynes said other types of seafood and fish, seaweed, walnuts, flax seeds, or chia seeds are good dietary sources of omega-3s. —Stephanie Brown, Verywell Health, 5 Mar. 2024

Don’t: Eat Raw Oysters That Aren’t Served on Ice While oysters served on rock salt or a bed of seaweed might look nice, Pirello says those setups are culinary red flags. —Kelsey Mulvey, Sunset Magazine, 11 Apr. 2024

And even then, it’s been obscured underneath layers of seaweed — a cash crop harvested by locals. —Brendan Rascius, Miami Herald, 5 Apr. 2024

What is sea moss good for? Sea moss is a type of seaweed that's often used as a supplement in gel, liquid, capsule or gummy forms. —Hannah Yasharoff, USA TODAY, 22 Mar. 2024

Feed Additives Innovative feed additives, such as red seaweed, could reduce livestock methane emissions by 26% to 98%, depending on the type of additive and how it is administered. —Paul Winters, Discover Magazine, 16 Mar. 2024

Word History

First Known Use

1577, in the meaning defined at sense 1a

Kids Definition

seaweed

noun

sea·​weed -ˌwēd 

: a plant growing in the sea

especially : a marine alga (as a kelp)