someone who is not well known, and who surprises people by winning a competition
In the 1955 golf championship, dark horse Jack Fleck defeated Ben Hogan.
BrE someone who does not tell people much about themselves, but who has surprising qualities or abilities
She's a dark horse. I didn't know she'd written a novel.
a racehorse about which little is known
1. Because of my dark skin, kids at school called me names; I often got mugged coming home from school. My diving made me feel good about myself when my peers made me feel stupid. 由于我肤色黑，常常遭到学校里孩子们的辱骂。放学回家时常常遭到欺负。尽管同龄孩子们让我觉得自己不如别人，但跳水却使我对自己有了信心。
2. But, as I walked out of the garage, KFC chicken in hand, a portly, unshaven young man in a stocking cap and dark nylon jacket emerged from the shrub by the parking pad and put his pistol between my eyes. 可是当我手里拿着肯德基炸鸡走出车库时，一个肥壮、留着短髭、头戴绒线帽、身穿深色尼龙夹克的年轻人从停车处旁边的灌木丛中钻出来，把手枪顶在我的双眼之间。
3. But also, I was presenting to her one more particularly fine achievement: my own dark-eyed, dark-skinned, dark-haired daughter, whom my grandmother had never met. 但同时，我还要向她展示另一样特别出色的成就：我那黑眼睛、黑皮肤、黑头发的女儿，外婆还从来没有见过她呢。
4. We bought a chestnut horse. 我们买了匹栗褐色马。
5. With this watch you can tell time in the dark because its hands and dial are luminous. 用这只表你可以在黑暗中看时间，因为它的针和针盘都是会发亮的。
6. When it grew dark, she turned a suitcase into a bed and put the children inside it, covering them with all the clothes she could find. 天黑下来的时候，她把提箱当作小床，把两个孩子放了进去，又把所有能找到的衣服都盖在了孩子们身上。
7. We are in Montreal, in an echoing, dark train station, and we are squeezed together on a bench waiting for someone to give us some guidance. 我们到了蒙特利尔，呆在一个嘈杂的、黑暗的火车站里, 紧紧地挤在一起 坐在一条长凳上，等着有人来给我们带路。
8. While praying one morning he was kicked by a horse. 有一天早晨，他在祈祷的时候还被马踢了一下。
9. While he chatted with other tourists, I exchanged polite conversation in the dark with a man seated in front of me, a Belgian who spoke fluent English. 他跟其他游客聊着天，我则在黑暗中礼貌地跟一位坐在我前面的男士谈话。他是位比利时人，讲一口流利的英语。
10. We can't really call a friend to say we got a parcel from our sister, or it's getting dark earlier now, or we don't trust that new Supreme Court justice. 我们不会真打电话给一位朋友，告诉他我们收到了姐姐的一个包裹，或者说现在天黑得比较早，或者说我们不信任最高法院新来的法官。