reef
noun
a ridge of rocks or sand, often of coral debris, at or near the surface of the water.
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reef
1 American
[reef]
/ rif /
noun
-
a ridge of rocks or sand, often of coral debris, at or near the surface of the water.
-
Mining. a lode or vein.
reef
2
American
[reef]
/ rif /
noun
verb (used with object)
-
reefs,
present (3rd person singular)
-
reefed,
past participle, past
-
reefing
present participle
-
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 ).
Reef
1
British
/ riːf /
noun
-
another name for the Great Barrier Reef
-
another name for the Witwatersrand
reef
2
British
/ riːf /
noun
-
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
reef
3
British
/ riːf /
noun
verb
-
to reduce the area of (sail) by taking in a reef
-
(tr) to shorten or bring inboard (a spar)
reef
Scientific
/ rēf /
-
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
Other Word Forms
Derived Forms
Inflected Forms
Participles
Conjugated Forms
Present
-
reefsimple
-
reefssimple
-
have reefedperfect
-
has reefedperfect
-
am reefingprogressive
-
are reefingprogressive
-
is reefingprogressive
-
have been reefingperfect progressive
-
has been reefingperfect progressive
Past
-
reefedsimple
-
had reefedperfect
-
was reefingprogressive
-
were reefingprogressive
-
had been reefingperfect progressive
Future
Etymology
Origin of reef1
1575–85; earlier riff ( e ) < Dutch rif
Origin of reef2
1350–1400; Middle English refe (noun) < Dutch reef
Explanation
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."
Vocabulary lists containing reef
Physical Geography - Introductory
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Physical Geography - Middle School
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Physical Geography - High School
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
See Examples For:
It can also help reconstruct the ecology of early Paleozoic oceans, when crinoids were among many early animal groups flourishing in reef ecosystems.
From Science Daily ● Aug. 21, 2026
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
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
The 39-year-old man died from a critical head injury after he was attacked while spearfishing at Kennedy Shoal, an offshore reef, Queensland police said.
From Barron's ● May 24, 2026
It sailed out through the reef to the deeper dark ocean, and Jack turned to wave and Nim waved back, though she knew he couldn’t see.
From "Nim’s Island" by Wendy Orr
She just presented “Terms of Agreement” at the Santa Monica performance space Highways after starting the rehearsal process through a CalArts-run residency at the Reef in downtown L.A.
From Los Angeles Times ● Jun. 30, 2026
This is why China is building out Antelope Reef at such a rapid pace, says Ray Powell, the director of Sealight, which is based in Stanford University and monitors the South China Sea.
From BBC ● Jun. 3, 2026
Outposts built before Antelope Reef drew significant international attention.
From The Wall Street Journal ● May 15, 2026
The team combined satellite measurements of ocean surface temperatures from the Coral Reef Watch system with on site reef surveys and aerial observations collected worldwide.
From Science Daily ● Feb. 12, 2026
Ayn said she would scuba dive the Great Barrier Reef until she either ran out of air or got eaten by a great white.
From "Scythe" by Neal Shusterman
Arabic texts as far back as the 15th century codified the discipline of navigation, though ship captains sailed the reefs from memory, using poems rather than maps to recall notable landmarks.
From The Wall Street Journal ● Aug. 6, 2026
"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
Wildfires, floods, melting ice caps, heat waves, the bleaching of ocean reefs.
From Los Angeles Times ● Jun. 18, 2026
“Then, listen, Captain Bowditch. There’s a lot I’d better tell you. When you hit the coral reefs off Sumatra...”
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
The firm has only reefed 12 of the 60 Gulf of Mexico platforms it has decommissioned.
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
There was a sailboat with rusty red sails reefed around the booms of the fore and aft masts.
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
The federal Bureau of Safety and Environmental Enforcement urges states to issue reefing permits.
From Economist ● Jun. 12, 2014
State coffers gain: oil firms typically hand over half the money they save by reefing.
From Economist ● Jun. 12, 2014
But the science regarding the safety of artificial reefing is still being developed.
From Time Magazine Archive
“Me fall off of a house! Me that’s hung by my eyebrows, reefing sail in a storm! Fix me up good, Doc, so I can be ready when the Putnam sails.”
From "Carry On, Mr. Bowditch" by Jean Lee Latham
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.
