Real Dictionary

nightingale
countable noun: A nightingale is a small brown bird. The male, which can be heard at night, sings beautifully.

Nightingale in American English
any of various small European thrushes (genus Luscinia) with a russet back and buff to white underparts: the male is known for its varied, melodious singing, esp. at night during the breeding season
Florence1820-1910; Eng. nurse in the Crimean War: regarded as the founder of modern nursing
noun: any of several small, Old World, migratory birds of the thrush family, esp Luscinia megarhynchos, of Europe, noted for the melodious song of the male, given chiefly at night during the breeding season

nightingale in British English
noun: a brownish European songbird, Luscinia megarhynchos, with a broad reddish-brown tail: well known for its musical song, usually heard at night
noun: Florence, known as the Lady with the Lamp. 1820–1910, English nurse, famous for her work during the Crimean War. She helped to raise the status and quality of the nursing profession and founded a training school for nurses in London (1860)