1 PHRASAL VERB 背着(配偶、性伴侣)乱搞;对(配偶、性伴侣)不忠 If someone cheats on their husband, wife, or partner, they have a sexual relationship with another person. 背着(配偶、性伴侣)乱搞;对(配偶、性伴侣)不忠 [informal]
2 PHRASAL VERB 违背,违反(约定);逃避(纳税) If someone cheats on something such as an agreement or their taxes, they do not do what they should do under a set of rules. 违背,违反(约定);逃避(纳税) [mainly US]