From The Collaborative International Dictionary of English v.0.48 [gcide]:
Reef \Reef\ (r[=e]f), 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 (Zool.), any stony coral which contributes
material to the formation of coral reefs.
Reef heron (Zool.), any heron of the genus Demigretta;
as, the blue reef heron (Demigretta jugularis) of
Australia.
[1913 Webster]