sea urchin

American  

noun

• sea urchins
  plural

1. any echinoderm of the class Echinoidea, having a somewhat globular or discoid form, and a shell composed of many calcareous plates covered with projecting spines.

2. a tall evergreen shrub or small tree, Hakea laurina, of Australia, having narrow leaves and dense, globe-shaped clusters of crimson flowers with long yellow stamens.

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sea urchin British  

noun

1. any echinoderm of the class Echinoidea, such as Echinus esculentus ( edible sea urchin ), typically having a globular body enclosed in a rigid spiny test and occurring in shallow marine waters

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Other Word Forms

Noun Inflected Forms

• sea urchins
  plural

Etymology

Origin of sea urchin

First recorded in 1585–95

Example Sentences

See Examples For:

sea urchin

Ora King salmon crudo was dressed in passionfruit aguachile with Tabasco oil, while a uni carbonara used creamy sea urchin in place of guanciale, finished with smoked trout roe.

From Salon ● Feb. 2, 2026

Her fossilized sea urchin, from a beach on the Red Sea, “responds by radiating its own inner joy at being found and loved too,” whispering: “We are two cyclical beings, each with their own story.”

From The Wall Street Journal ● Jan. 16, 2026

When sea urchin populations grow too large, however, especially if their natural predators are heavily hunted or overfished, the balance can flip.

From Science Daily ● Dec. 12, 2025

Ninety-five percent of Northern California’s kelp forest has been displaced by sea urchin “barrens” since the West Coast’s marine heat wave in 2014, ’15 and ’16, when water temperature averaged 7 degrees above normal.

From Los Angeles Times ● Jun. 5, 2024

“They have a rare species of sea urchin that you find nowhere else in the Archipelago. The spines are a foot long, and they turn red in the presence of predators.”

From "Impossible Creatures" by Katherine Rundell