Reef (rēf), n. [Akin to D. rif, G. riff, Icel. rif, Dan. rev; cf. Icel. rifa rift, rent, fissure, rifa to rive, bear. Cf. Rift, Rive.] 1. A chain or range of rocks lying at or near the surface of the water. See Coral reefs, under Coral.
[1913 Webster]

2. (Mining.) A large vein of auriferous quartz; -- so called in Australia. Hence, any body of rock yielding valuable ore.
[1913 Webster]

Reef builder (Zoöl.), any stony coral which contributes material to the formation of coral reefs. -- Reef heron (Zoöl.), any heron of the genus Demigretta; as, the blue reef heron (Demigretta jugularis) of Australia.
[1913 Webster]

Reef, v. t. [imp. & p. p. Reefed (rēft); p. pr. & vb. n. Reefing.] (Naut.) To reduce the extent of (as a sail) by rolling or folding a certain portion of it and making it fast to the yard or spar. Totten.
[1913 Webster]

To reef the paddles, to move the floats of a paddle wheel toward its center so that they will not dip so deeply.
[1913 Webster]