Meaning of reef

reef

1. a ridge of rocks or sand, often of coral debris, at or near the surface of the water.
2. a lode or vein.

reef

1. a part of a sail that is rolled and tied down to reduce the area exposed to the wind.

1. to shorten (sail) by tying in one or more reefs.
2. to reduce the length of (a topmast, a bowsprit, etc.), as by lowering, sliding inboard, or the like.
3. to pull (old oakum) out of seams, as with a rave hook (often fol. by out).