Reef, n.  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.
 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.