形容词

1. 背信弃义的;不忠实的;不诚实的
    If you say that someone is faithless, you mean that they are disloyal or dishonest.

1. having the character of, or characteristic of, a traitor

    e.g. the faithless Benedict Arnold
           a lying traitorous insurrectionist

    Synonym: traitorousunfaithfultreasonabletreasonous