coral reef

American  

noun

1. a reef composed mainly of coral and other organic matter of which parts have solidified into limestone.

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coral reef British  

noun

1. a marine ridge or reef consisting of coral and other organic material consolidated into limestone

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coral reef Scientific  

1. A mound or ridge of living coral, coral skeletons, and calcium carbonate deposits from other organisms such as calcareous algae, mollusks, and protozoans. Most coral reefs form in warm, shallow sea waters and rise to or near the surface, generally in the form of a barrier reef, fringing reef, or atoll. Coral reefs grow upward from the sea floor as the polyps of new corals cement themselves to the skeletons of those below and in turn provide support for algae and other organisms whose secretions serve to bind the skeletons together. The resulting structure provides a critical habitat for a wide variety of fish and marine invertebrates. Coral reefs also protect shores against erosion by causing large waves to break and lose some of their force before reaching land. The Great Barrier Reef off the northeastern coast of Australia extends for some 2,000 km (1,240 mi), making it the world's largest coral reef.

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coral reef Cultural  

1. A formation, at or near the surface of tropical waters, formed by skeletal deposits of corals, a form of sea life.

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Discover More

Atolls — ring-shaped islands that nearly or entirely enclose a lagoon — are coral reefs.

Coral reefs form a protective environment for a wide variety of marine animals.

Coral reefs are very sensitive to chemical pollution and changes in temperature and are considered to be in danger from environmental stress.

The largest coral reef is the Great Barrier Reef of Australia.

Etymology

Origin of coral reef

First recorded in 1735–45

Example Sentences

The film cuts to a hummingbird sipping nectar from a flower on a cactus, a sea turtle floating over a coral reef, pink flamingos on a green lake, a snowflake, a butterfly.

From The Wall Street Journal • Apr. 16, 2026

The Great Barrier Reef, the world's biggest coral reef system on the north-east coast, is rightly recognised as a Unesco World Heritage Site.

From BBC • Jul. 22, 2025

A coral reef is normally built out of lots of colonies of different kinds.

From NewsForKids.net • Nov. 27, 2024

Even the recent Red List assessment that found over two-fifths of coral reef species threatened with extinction added there are some species where data is so deficient that a risk category cannot be assigned.

From Salon • Nov. 21, 2024

Out there, perhaps a mile away, the white surf flinked on a coral reef, and beyond that the open sea was dark blue.

From "Lord of the Flies" by William Golding

Related Words

• atoll
• beach
• shoal