step out on someone
phrasal verb with step verb [ I + adv/prep ] uk/step/ us/step/ -pp-
US informal
对（伴侣）不忠
If you step out on your husband, wife, or usual sexual partner, you have sexual relationships with people other than them.
江苏热线英汉汉英双解词典包含207361条英汉翻译词条，涵盖了常用英语单词及词组短语的翻译及用法，是英语学习的必备工具。