Meaning

• A chain or range of rocks, sand, or coral lying at or near the surface of the water.

• A large vein of auriferous quartz; hence, any body of rock yielding valuable ore.

• A portion of a sail rolled and tied down to lessen the area exposed in a high wind.

• A reef knot.

Meaning

• To take in part of a sail in order to adapt the size of the sail to the force of the wind.

• To pull or yank strongly, especially in relation to horse riding.

• (of paddles) To move the floats of a paddle wheel toward its center so that they will not dip so deeply.

  "Reef the paddles."