Noun
backstabber (plural backstabbers)
A traitor or hypocrite, such as a co-worker or friend assumed trustworthy but who figuratively attacks when one's back is turned.
Synonym: snake in the grass
Hyponym: smiling assassin
Pentagon had Rush down with a backstabber. Source: Internet
Perhaps Nelle could suggest that even if it’s true, she doesn’t need a backstabber like Nina for a mom. Source: Internet