✔ 最佳答案
steal one's girlfriend
更口語化的講法是 bird-dogging
When another guy steals a girl from her boyfriend. It is used as a nasty,unethical, and immoral tactic. It is especially bad when the guy is (was) a good friend of yours and the girl is your best friend.
Joe was bird dogging Peter when he stole Megan from him right behind his back.
http://www.urbandictionary.com/define.php?term=bird+dogging