形容词

1. 不忠的；通奸的
If someone is unfaithful to their lover or to the person they are married to, they have a sexual relationship with someone else.

1. not trustworthy

e.g. an unfaithful reproduction

2. not true to duty or obligation or promises

e.g. an unfaithful lover

3. having sexual relations with someone other than your husband or wife, or your boyfriend or girlfriend

e.g. her husband was unfaithful

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

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

Synonym: faithlesstraitoroustreasonabletreasonous