Infidelity or being unfaithful in a relationship can be devastating. It can shatter trust and lead to broken hearts. It is important to understand the different synonyms for the word "is unfaithful" in order to address the issue properly. Some common synonyms include, "cheats," "deceives," "betrays," "goes behind someone's back," "commits adultery," "plays around," and "has an affair." These words all refer to the act of betraying a partner's trust by engaging in sexual or emotional relationships with someone else. It is important to have open communication with your partner if you suspect infidelity is occurring in order to address the issue and work towards a healthier relationship.