Definition of reef

• n. - A chain or range of rocks lying at or near the surface of the water. See Coral reefs, under Coral.
• n. - A large vein of auriferous quartz; -- so called in Australia. Hence, any body of rock yielding valuable ore.
• 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.
• 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.