reef

1 of 3

noun (1)

ˈrēf 

1

: a part of a sail taken in or let out in regulating size

2

: reduction in sail area by reefing

reef

2 of 3

verb

reefed; reefing; reefs

transitive verb

1

: to reduce the area of (a sail) by rolling or folding a portion

2

: to lower or bring inboard (a spar) wholly or partially

intransitive verb

: to reduce a sail by taking in a reef

reefable

ˈrē-fə-bəl 

adjective

reef

3 of 3

noun (2)

1

a

: a chain of rocks or coral or a ridge of sand at or near the surface of water compare atoll, barrier reef

b

: a hazardous obstruction

2

: lode, vein

reefy

ˈrē-fē 

adjective

Examples of reef in a Sentence

Recent Examples on the Web

Noun

With most tropical reefs expected to face conditions like the Gulf’s by 2100—and already faltering under increasingly frequent marine heat waves—that makes the Gulf’s coral a source of valuable genetic information about resilience that could have implications for the rest of the world’s reefs. —Meghan Bartels, Scientific American, 14 May 2026

Most of the island sits within a national park and there is snorkeling along the adjacent reef, rainforest hiking, and plenty of quiet, sandy beach. —Evie Carrick, Travel + Leisure, 14 May 2026

Verb

The Halekulani's Honey & Coral Project addresses Okinawa’s crippling red soil erosion – runoff that smothers reefs – by stabilizing the soil with vegetation. —Christopher Elliott, Forbes.com, 11 Jan. 2026

The rig is also designed to be reefed while preserving optimal balance between hull and appendages, meaning the yacht performs reliably in a wide range of conditions. —Rachel Cormack, Robb Report, 30 June 2025

Word History

Etymology

Noun (1)

Middle English riff, from Old Norse rif; probably akin to Old Norse rīfa to rend — more at rive

Noun (2)

Dutch rif, from Middle Dutch, from Old Norse, literally rib; akin to Old English ribb rib — more at rib

First Known Use

Noun (1)

14th century, in the meaning defined at sense 1

Verb

1670, in the meaning defined at transitive sense 1

Noun (2)

1584, in the meaning defined at sense 1a

Phrases Containing reef

• barrier reef
• coral reef
• reef knot
• whitetip reef shark

Rhymes for reef

• beef
• brief
• chief
• fief
• grief
• leaf
• lief
• reif
• seif
• sheaf
• thief
• belief

Kids Definition

reef

1 of 3 noun

ˈrēf 

1

: a part of a sail taken in or let out in regulating size

2

: the reduction in sail area made by reefing

reef

2 of 3 verb

: to reduce the area of (a sail) by rolling or folding a portion

reef

3 of 3 noun

: a chain of rocks or coral or a ridge of sand at or near the surface of water

Etymology

Noun

Middle English riff "reef of a sail"; of Norse origin

Noun

from Dutch rif "reef of rocks or sand"; of Scandinavian origin