backstabbingback‧stab‧bing /ˈbækstæbɪŋ/ noun [uncountable] 
the act of secretly doing bad things to someone else, especially saying bad things about them, in order to gain an advantage for yourself—backstabber noun [countable]
the act of secretly doing bad things to someone else, especially saying bad things about them, in order to gain an advantage for yourself—backstabber noun [countable]