turncoat

[turn-koht] /ˈtɜrnˌkoʊt/
noun
1.
a person who changes to the opposite party or faction, reverses principles, etc.; renegade.
Origin
1550-60; turn + coat
Examples from the web for turncoat
  • Mugwump thus became a term for a political turncoat.
  • Each, too, was accused of being a turncoat and evoked bitter political enmity.
British Dictionary definitions for turncoat

turncoat

/ˈtɜːnˌkəʊt/
noun
1.
a person who deserts one cause or party for the opposite faction; renegade
Word Origin and History for turncoat
n.

1550s, from turn (v.) + coat (n.). Originally one who tried to hide the badge of his party or leader. The expression to turn one's coat "change principles or party" is recorded from 1560s.