marked by deliberate deceptiveness especially by pretending one set of feelings and acting under the influence of another; "she was a deceitful scheming little thing"- Israel Zangwill; "a double-dealing double agent"; "a double-faced infernal traitor and schemer"- W.M.Thackeray; ambidextrous, deceitful, double-dealing, duplicitous, Janus-faced, double-faced, double-tongued
having two faces--one looking to the future and one to the past; Janus-faced
Janus the two-faced god
English Idioms Dictionary
disloyal, untrustworthy I think he is two-faced and can never be trusted.
