mistress; the other woman; home wrecker;
举例：
Immature woman abuses the husband's mistress when he has an extramarital affair;
2.报道称，一位女画家昨天早晨将老公和“小三”捉奸在床，气愤的她把此事发在了自己的微博上，并持续“直播”她与老公以及“小三”之间的交锋。
The woman, a painter, became so furious, she revealed the affair with a Twitter post and live-tweeted the fight between her, her husband and his mistress.
3.网络写手们用各式各样的称谓来形容郭美美：炫富、无耻、小三、丑陋等等。
Online writers have taken to calling Guo a variety of names: show off,shameless, mistress, ugly and others.
瞪样的胖子
