From Longman Dictionary of Contemporary Englishtwo-facedˌtwo-ˈfaced adjective informal PRETENDchanging what you say according to who you are talking to, in a way that is insincere and unpleasant – used to show disapproval He’s a two-faced liar.
Examples from the Corpus
two-faced• Whoever you blame on the scum transfer fiasco he came out of it as a two-faced hypocrite.• He was at his most two-faced in his dealings with Turgenev.• He was such a two-faced little man that finding these hysterically funny didn't feel wrong.• I've never met anyone so two-faced: she's sweet and charming to your face, and then goes and complains about you to the boss!• I wanted to put all that two-faced stuff behind us and settle down with Mary-Claude to live a half-way normal life.• The Government's attitude is two-faced - they are also devoting all their energies to preventing the directive from coming into force.• Barb is the most two-faced woman I've ever met. 