turncoat
Definitions
A person who deserts one party or cause in order to join an opposing one.
A traitor who switches allegiance.
Examples
The general was branded a turncoat after he defected to the enemy side during the heat of the battle.
He was once a loyal member of the party, but his colleagues labeled him a turncoat when he switched his political allegiance.
No one in the resistance trusted the turncoat, fearing he would reveal their secret hideout to the authorities.
Synonyms
traitor defector renegade deserter apostate quisling betrayer
Antonyms
loyalist patriot stalwart faithful adherent supporter devotee