The Collaborative International Dictionary
jerfalcon
Gyrfalcon \Gyr"fal`con\ (j[~e]r"f[add]`k'n), 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 Falco Islandicus, both of which are circumpolar. The black and the gray are varieties of the former. See Illust. of Accipiter.
Wiktionary
jerfalcon
n. (alternative form of gyrfalcon English)