1. a. A rocklike deposit consisting of the calcareous skeletons secreted by various marine invertebrates, chiefly anthozoans. Coral deposits often accumulate to form reefs or islands in warm seas.
b. A polyp or colony of polyps of any of the numerous anthozoans that secrete a hard or flexible skeleton, especially the reef-building hard corals.
c. A polyp or colony of polyps of any of various hydrozoans that secrete hard skeletons, such as the fire corals.
d. The hard skeleton of various corals, especially of red corals of the genus Corallium, used to make jewelry and ornaments.
e. An object made of this material.