Noun

Singular reef

Plural reefs

reef (plural reefs)

1. A chain or range of rocks, sand, or coral lying at or near the surface of the water.
2. (Australian) & (South Africa) A large vein of auriferous quartz; hence, any body of rock yielding valuable ore.
3. (nautical) A portion of a sail rolled and tied down to lessen the area exposed in a high wind.
4. A reef knot.

Derived terms

• coral reef
• reef rash

Verb

Infinitive to reef

Third person singular reefs

Simple past reefed

Past participle reefed

Present participle reefing

to reef (third-person singular simple present reefs, present participle reefing, simple past and past participle reefed)

1. (nautical) To take in part of a sail in order to adapt the size of the sail to the force of the wind.

In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water (six fathoms or less at low water).

Many reefs result from abiotic processes—deposition of sand, wave erosion planning down rock outcrops, and other natural processes—but the best-known reefs are the coral reefs of tropical waters developed through biotic processes dominated by corals and calcareous algae. Artificial reefs such as shipwrecks are sometimes created to enhance physical complexity on generally featureless sand bottoms in order to attract a diverse assemblage of organisms, especially fish.