noun /ˈbɹɪ.tən,ˈbɹɪ.ʔn̩/
a) The United Kingdom.
The name of Britain [...] ought to answer every purpose, or if that be thought too condensed, it may be pluralized into The Britains. (The Times, 16 July 1874, 10/6, cited after OED).
b) Brittany.
The Britains struggles with the Scots and Picts [...] led to the Britains asking the Romans for help in constructing a great wall. (L. C. Lambdin and R. T. Lambdin, Companion to Old and Middle English Literature, 2002, p. 12.)
Wikipedia foundation.