unfaithful

Adjective

• not trustworthy
  • an unfaithful reproduction
    

• having the character of, or characteristic of, a traitor
  • the faithless Benedict Arnold
    
  • a lying traitorous insurrectionist
    

• having sexual relations with someone other than your husband or wife, or your boyfriend or girlfriend
  • her husband was unfaithful
    

• not true to duty or obligation or promises
  • an unfaithful lover
    

Related words

• Synonyms: 
  faithless , traitorous , treasonable , treasonous