sea cucumber Marine echinoderm found in rocky areas. It is a cylindrical animal with a fleshy body in five parts around a central axis; it has branched tentacles around the mouth. Edible species are smoked and dried. Species include the cotton-spinners (Holothuria spp.). Class Holothuroidea.

sea cu·cum·ber • n. an echinoderm (class Holothuroidea) that has a thick, wormlike body with tentacles around the mouth. They typically have rows of tube feet along the body.