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 ).
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
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 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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Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
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
Their goal was to investigate ancient reef ecosystems that once existed beneath an ocean covering the region millions of years ago.
From Science Daily ● Jun. 26, 2026
The speck was at Scarborough Shoal, a much-contested reef in the South China Sea, a maritime thoroughfare for about a quarter of the world’s seaborne trade.
From The Wall Street Journal ● Jun. 23, 2026
Ornithologist Simon Hugheston-Roberts spotted the western reef heron - more commonly found in southern Europe, Africa and parts of Asia - at Y Foryd in Caernarfon at 10:00 BST on Saturday.
From BBC ● Jun. 9, 2026
Then I saw the horrible thing anchored to the reef just below the waterline—an enormous mouth with slimy lips and mossy teeth the size of rowboats.
From "The Sea of Monsters" by Rick Riordan
Can you talk a little bit about Sublime Fest and your Sublime Reef Madness Cruise and how you came up with it?
From Los Angeles Times ● Jun. 11, 2026
Outposts built before Antelope Reef drew significant international attention.
From The Wall Street Journal ● May 15, 2026
The study -- conducted at the Shark Reef Marine Reserve in Fiji -- found that bull sharks do not simply mix randomly.
From Science Daily ● Mar. 17, 2026
Australia's Great Barrier Reef, for instance, saw peak heat stress increase each year between 2014 and 2017.
From Barron's ● Feb. 10, 2026
“Oh, and dig this. To show how much he cares about the ocean, he offers to throw a big fund-raising benefit for the Save the Reef Foundation on the Coral Queen.”
From "Flush" by Carl Hiaasen
"Lamu's mangroves, coral reefs and seagrass beds are not expendable. They support fisheries, livelihoods and coastal protection," the NGO said.
From Barron's ● Jul. 14, 2026
To reach those ancient reefs, the team had to cross extensive layers of rock known as turbidites.
From Science Daily ● Jun. 26, 2026
Oceanographers at the state-controlled Chinese Academy of Sciences said the platform was a temporary scientific research facility studying the shoal’s coral reefs.
From The Wall Street Journal ● Jun. 23, 2026
Wildfires, floods, melting ice caps, heat waves, the bleaching of ocean reefs.
From Los Angeles Times ● Jun. 18, 2026
Then Nat sent a man to the foremast to watch for the coral reefs, and two men to the chains to sound.
From "Carry On, Mr. Bowditch" by Jean Lee Latham
Divers and many fishermen want more to be reefed; shrimpers complain that reefs prevent them from dragging nets across parts of the ocean floor.
From Economist ● Jun. 12, 2014
Not one platform off California has been reefed.
From Economist ● Jun. 12, 2014
Currently, less than a tenth of America’s old oil and gas platforms are reefed.
From Economist ● Jun. 12, 2014
At this point the Regents reefed their sails, seemed unable to proceed.
From Time Magazine Archive
We have the sails tightly reefed and tied down.
From "Hole in My Life" by Jack Gantos
Part of that action is Patten’s realization that the sailor’s standard storm tactics—including reefing, heaving-to and lying a-hull—will not work in such an intense blow.
From The Wall Street Journal ● Dec. 8, 2025
State coffers gain: oil firms typically hand over half the money they save by reefing.
From Economist ● Jun. 12, 2014
Four years ago the Golden State passed a law allowing reefing.
From Economist ● Jun. 12, 2014
Finisterre's No. 2 Genoa blew out, but the crew replaced it and bore down while bigger yachts were reefing cautiously.
From Time Magazine Archive
Already reefing from the floods, Cahokia never recovered from the earthquake.
From "1491" by Charles C. Mann
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.
