Definition of sea urchin in US English:

sea urchin


  • A marine echinoderm that has a spherical or flattened shell covered in mobile spines, with a mouth on the underside and calcareous jaws. Many species are harvested for food.

    Class Echinoidea: several families and genera, and numerous species, including the Atlantic purple sea urchin (Arbacia punctulata, family Arbaciidae) and the green sea urchin (Strongylocentrotus drobachiensis, family Strongylocentrotidae)

    • ‘The inner shell of a sea urchin is a hollow globe, scored in five curved sections that taper at the ends into a small hole at the top and bottom.’
    • ‘The red sea urchin's body is domed above and flat below.’
    • ‘This sea urchin defends itself with two sets of mobile spines.’
    • ‘The sea urchin occupies an important evolutionary position with respect to vertebrates and humans.’
    • ‘The sea urchin is one of the few marine organisms whose genome has been sequenced.’


sea urchin

/ˈsi ˌərtʃən//ˈsē ˌərCHən/