1. a person who betrays a cause or allegiance; one who switches sides

Examples

• The senator was called a turncoat after switching political parties.
• Many viewed him as a turncoat for abandoning his former allies.
• She refused to be labeled a turncoat despite changing her position.
• The turncoat revealed secret information to the enemy.
• His friends felt betrayed when he became a turncoat.
• The company’s turncoat employee sold trade secrets to competitors.