What does the word turncoat mean?

Usage examples for turncoat

  1. I might have expected naught better from a turncoat foreign knave such as thee, who once joined in the councils of De Montfort, and then betrayed his friends to curry favor with the King. – The Outlaw of Torn by Edgar Rice Burroughs
  2. You're a little turncoat, that's what they say about you. – Every Soul Hath Its Song by Fannie Hurst