coral reef

American  

noun

• coral reefs
  plural

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.

Other Word Forms

Noun Inflected Forms

• coral reefs
  plural

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Etymology

Origin of coral reef

First recorded in 1735–45

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Example Sentences

See Examples For:

coral reef

In the first global assessment of its kind, the world authority on threatened wildlife classified 96 percent of the planet's coral reef systems as "critically endangered" -- its highest risk category.

From Barron's ● Oct. 22, 2026

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

Coastal species like frogfish, which live in diverse and productive coral reef environments, exhibited much lower rates of evolutionary change than their counterparts in the deep sea.

From Science Daily ● Dec. 2, 2024

A New Zealand warship which crashed into a coral reef before it caught fire and sank had been left on autopilot, an official inquiry has found.

From BBC ● Nov. 29, 2024

At the one extreme was Henderson Island, an old coral reef raised above sea level and devoid of stone Other than limestone.

From "Guns, Germs, and Steel: The Fates of Human Societies" by Jared M. Diamond

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Related Words

• atoll
• beach
• shoal

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