\Gyr"fal`con\, n. [OE. gerfaucon, OF. gerfaucon, LL.
gyrofalco, perh. fr. L. gyrus circle + falco falcon, and
named from its circling flight; or cf. E. gier-eagle. See
{Gyre}, n., {Falcon}.] (Zo["o]l.)
One of several species and varieties of large Arctic falcons,
esp. {Falco rusticolus} and the white species {F.
Islandicus}, both of which are circumpolar. The black and the
gray are varieties of the former. See Illust. of {Accipiter}.
[Written also {gerfalcon}, {gierfalcon}, and {jerfalcon}.]