infidelity
noun [ C or U ] uk/ˌɪn.fɪˈdel.ə.ti/ us/ˌɪn.fəˈdel.ə.t̬i/
（夫妇间的）不忠实，不贞行为
(an act of) having sex with someone who is not your husband, wife, or regular sexual partner
marital/sexual infidelity 婚姻／性方面的不忠
She could not forgive his many infidelities. 她不能原谅他的诸多不忠行为。
Synonym: faithlessness (NOT LOYAL)
Opposites: faithfulnessfidelity