Definition of grey falcon in US English:

grey falcon

(US gray falcon)

noun

  • 1(In early use) the hen harrier, Circus cyaneus, or the peregrine falcon, Falco peregrinus.

  • 2(In later use) F. hypoleucos of arid regions of Australia.

Origin

Late 17th century; earliest use found in John Ray (1627–1705), naturalist and theologian.