1.NounSomeone who violates an allegiance and betrays their country; someone guilty of treason; one who, in breach of trust, delivers their country to an enemy, or yields up any fort or place entrusted to their defense, or surrenders an army or body of troops to the enemy, unless when vanquished.
"After World War I, the communists and Jews were accused to be traitors by the German right wing (the "stab-in-the-back myth"), ultimately culminating in their persecution and massacre."
2.NounSomeone who takes arms and levies war against their country; or one who aids an enemy in conquering their country.
3.NounOne who betrays any confidence or trust.
4.VerbTo act the traitor toward; to betray; to deceive.