a ridge of rocks or sand, often of coral debris, at or near the surface of the water.
Mining. a lode or vein.
to shorten (sail) by tying in one or more reefs.
to reduce the length of (a topmast, a bowsprit, etc.), as by lowering, sliding inboard, or the like.
to pull (old oakum) out of seams, as with a rave hook (often followed byout ).
to reduce the area of (sail) by taking in a reef
(tr) to shorten or bring inboard (a spar)
another name for the Great Barrier Reef
another name for the Witwatersrand
a ridge of rock, sand, coral, etc, the top of which lies close to the surface of the sea
a ridge- or mound-like structure built by sedentary calcareous organisms (esp corals) and consisting mainly of their remains
a vein of ore, esp one of gold-bearing quartz
A strip or ridge of rocks, sand, or coral that rises to or near the surface of a body of water.
See more at coral reef
1575–85; earlier riff ( e ) < Dutch rif
1350–1400; Middle English refe (noun) < Dutch reef
A reef is a raised area on the ocean floor that's made of rock, coral, or sand. If you are a scuba diver, head to a coral reef to check out the diverse marine life. A barrier reef is one that surrounds an island and creates a lagoon between the reef and the beach. When this type of reef attracts diverse ocean life, it can be popular with snorkelers and scuba divers. When you're sailing, a reef is a section of the sail that you can roll up when necessary — and to reef is to roll up a reef. Both meanings share an Old Norse root, rif, "ridge under the water."
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In one dramatic episode, an American ship, the Philadelphia, was grounded on a reef and captured, but in 1804, the Americans launched a successful mission to rescue her with no casualties.
From Salon • Jul. 4, 2026
Cleaner fish remove parasites from larger reef fish and receive a meal in return.
From Science Daily • Jun. 20, 2026
Kennedy Shoal is a well-known fishing reef in deep water.
From Barron's • May 24, 2026
The “underwater city” of a barrier reef bustles with activity, with vibrantly patterned fish darting busily between corals and sea sponges.
From The Wall Street Journal • May 22, 2026
Whatever it is, it’s hovering above the reef break.
From "Clairboyance" by Kristiana Kahakauwila
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
