It's hard to get shorter than traitor, which is only two syllables. "Sneak", "grass", or "fink" might do.
The word "traitor" in German is "Verräter".
Traitor
The traitor sold secrets to the enemy.
he is a traitor. Traitors are punished very harshly.
That is the definition of the word traitor.
The word "traitor" is 'uragirimono' in Japanese.
Traitor in Russian is предатель. (predatel)
she was a traitor to the cat family until she found out she is a cat.
One man's traitor is another man's hero.
kha'en:خائن
Antigone's meaning of the word traitor is a daughter that buries her brother's body.
Benedict Arnold was a traitor to the United States during the Revolutionary War.