adulterous

Adjective

• not faithful to a spouse or lover
  • adulterous husbands and wives
    
  • a two-timing boyfriend
    

• characterized by adultery
  • an adulterous relationship
    
  • extramarital affairs
    
  • the extracurricular activities of a philandering husband
    

Related words

• Synonyms: 
  cheating(a) , two-timing(a) , extramarital , extracurricular