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

The western Atlantic had a significant increase in sargassum from November as a result of both local blooms and seaweed traveling west from the waters off Africa. —Bill Kearney, Sun Sentinel, 14 Jan. 2025

The juniper is still present and accounted for, along with notes of citrus that contrast nicely with the oyster and seaweed flavors. —Tony Sachs, Forbes, 13 Jan. 2025

The brown rice, beans and seaweed are all good sources of fiber. —Michiko Tomioka, Contributor, CNBC, 5 Jan. 2025

From seaweed wraps to hot stone massages, the biggest decision here is which treatment to try next. —Meagan Drillinger, Travel + Leisure, 1 Jan. 2025

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)