Any of numerous corals having a hard skeleton of calcium carbonate; (now) specifically those constituting the order Scleractinia, typically found on coral reefs; also as a mass noun.
Origin
Early 19th century.
Definition of hard coral in US English:
hard coral
noun
Any of numerous corals having a hard skeleton of calcium carbonate; (now) specifically those constituting the order Scleractinia, typically found on coral reefs; also as a mass noun.