reef: see coral reefcoral reefs,
limestone formations produced by living organisms, found in shallow, tropical marine waters. In most reefs, the predominant organisms are stony corals, colonial cnidarians that secrete an exoskeleton of calcium carbonate (limestone).
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.
a sharp underwater or above-water elevation in the sea floor in shallow water that hampers navigation. Reefs are formed either by the erosion of the bottom and coasts of the sea or by colonies of coral.
a device for reducing sail area during a strong wind. The reef is usually a series of bands threaded through the sail, by means of which the sail is folded up when the boom or yard is taken up—that is, the sail is reefed, or taken in. Sails may have from one to four reefs.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
A ridge- or moundlike layered sedimentary rock structure built almost exclusively by organisms.
An offshore chain or range of rock or sand at or near the surface of the water.
A major ore trend or ore body.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
1. a ridge of rock, sand, coral, etc., the top of which lies close to the surface of the sea
2. a ridge- or mound-like structure built by sedentary calcareous organisms (esp corals) and consisting mainly of their remains
the part gathered in when sail area is reduced, as in a high wind
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005