Noah Webster's Dictionary 1. (n.) A chain or range of rocks lying at or near the surface of the water. See Coral. 2. (n.) A large vein of auriferous quartz; -- so called in Australia. Hence, any body of rock yielding valuable ore. 3. (v. t.) 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. 4. (v. t.) 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.

Multi-Version Concordance Reef (1 Occurrence) Acts 27:41 But coming to a place where two seas met, they ran the vessel aground. The bow struck and remained immovable, but the stern began to break up by the violence of the waves. (See NAS)