/ˌɪnfɪˈdeləti ||; ˌɪnfəˈdɛlətɪ/noun [U] [C] (plural infidelities) the act of not being faithful to your wife or husband by having a sexual relationship with sb else （夫妇间）不忠诚或不贞行为 ☞ A less formal word is unfaithfulness. 不大正式的场合用unfaithfulness。