Reef \Reef\ (r?f), n. [Akin to D. rif, G. riff, Icel. rif, Dan. rev; cf. Icel. rifa rift, rent, fissure, rifa to rive, bear. Cf. Rift, Rive.]

1. A chain or range of rocks lying at or near the surface of the water. See Coral reefs, under Coral.

2. (Mining.) A large vein of auriferous quartz; -- so called in Australia. Hence, any body of rock yielding valuable ore.

Reef builder (Zo["o]l.), any stony coral which contributes material to the formation of coral reefs.

Reef heron (Zo["o]l.), any heron of the genus Demigretta; as, the blue reef heron (D. jugularis) of Australia.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Reef \Reef\, n. [Akin to D. reef, G. reff, Sw. ref; cf. Icel. rif reef, rifa to basten together. Cf. Reeve, v. t., River.]

(Naut.) That part of a sail which is taken in or let out by means of the reef points, in order to adapt the size of the sail to the force of the wind.

Note: From the head to the first reef-band, in square sails, is termed the first reef; from this to the next is the second reef; and so on. In fore-and-aft sails, which reef on the foot, the first reef is the lowest part. --Totten.

Close reef, the last reef that can be put in.

Reef band. See Reef-band in the Vocabulary.

Reef knot, the knot which is used in tying reef pointss. See Illust. under Knot.

Reef line, a small rope formerly used to reef the courses by being passed spirally round the yard and through the holes of the reef. --Totten.

Reef points, pieces of small rope passing through the eyelet holes of a reef-band, and used reefing the sail.

Reef tackle, a tackle by which the reef cringles, or rings, of a sail are hauled up to the yard for reefing. --Totten.

To take a reef in, to reduce the size of (a sail) by folding or rolling up a reef, and lashing it to the spar.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Reef \Reef\, v. t. [imp. & p. p. Reefed (r[=e]ft); p. pr. & vb. n. Reefing.]

(Naut.) To reduce the extent of (as a sail) by roiling or folding a certain portion of it and making it fast to the yard or spar. --Totten.

To reef the paddles, to move the floats of a paddle wheel toward its center so that they will not dip so deeply.

Source: Webster's Revised Unabridged Dictionary (1913)