(1):

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

(2):

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

(3):

(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.

(4):

(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.