What does "shearwater" mean?

Shearwater: Any one of numerous species of long-winged oceanic birds of the genus Puffinus and related genera. They are allied to the petrels, but are larger. The Manx shearwater (P. Anglorum), the dusky shearwater (P. obscurus), and the greater shearwater (P. major), are well-known species of the North Atlantic. See Hagdon.