black sheep:Black sheep is an idiom used to describe an odd or disreputable member of a group, especially within a family.用汉语来说，就是“败家子，败类，有辱门风人”，也可以说是“害群之马”。 这个表达来源于18世纪的一句谚语: "There is a black sheep in every flock" 意思是每群白羊中必有一只黑色的。因为那时黑绵羊的毛不容染色，所以黑绵羊的价钱也比不上白羊的，黑色的羊就特别不受待见。而且，黑色在欧洲更是寓意魔鬼与不幸的颜色。
一起来看两个例句吧：
May is the black sheep in the family because she is an artist whereas everyone else is an economist.
梅有辱门风，因为她是艺术家，而家族其他人都是经济学家。Chinese Men's National Soccer Team is regarded as the black sheep of the Chinese national teams. 中国男足被认为是中国国家体育队的害群之马。
此外，说起“黑羊”，很多人会想到“黑马”，谁不想做一匹逆流而上的“黑马”呢？
但“黑马”可不是black horse，正确的说法是dark horse哦！我们来看一下权威的解释：dark horse:A candidate or competitor about whom little is known but who unexpectedly wins or succeeds.鲜为人知的候选人或竞争者，意外地获胜或成功。
来一个例句：
Don't think you'll beat him easily, he may be a dark horse. 不要以为你会轻而易举地胜过他，他可能是出人意料的高手。
