a dark horse

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dark horse

1. Someone who unexpectedly wins a competition. Nobody thought Cheri could win the race after breaking her leg last year, but she turned out to be a dark horse and took first place. No one thought the brash newcomer would be a threat to the established candidates, but he's turning out to be a real dark horse in this campaign.
2. Someone whose skills, abilities, plans, or intentions are or had been unapparent to others. Primarily heard in UK, Australia. Angela was suddenly viewed as a dark horse when she displayed her beautiful sculptures at the art fair. Nobody knew she had such artistic talent.
See also: dark, horse
Farlex Dictionary of Idioms. © 2022 Farlex, Inc, all rights reserved.

a dark horse

1. If you describe someone as a dark horse, you mean that you have just discovered something about them, especially a skill or an achievement, that they had not told you about. I didn't know Clare could sing like that. She's a dark horse. What a lot of friends from the past you have — you really are a dark horse, Robert!
2. A dark horse is someone who wins a contest, race, etc when they were not expected to. Czech Karel Novacek, the dark horse of the international tennis circuit, beat his opponent 7-5, 6-2, 6-4. Note: You can also use dark horse before a noun. William Randolph Hearst had briefly been a dark horse candidate for President in 1908. Note: This expression may refer to a horse which people do not know very much about, so that it is difficult to predict how well it will do in a race.
See also: dark, horse
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012

a dark horse

a person, especially a competitor, about whom little is known.
The expression was originally horse-racing slang. The earliest recorded use was by Benjamin Disraeli in 1831 : ‘A dark horse, which had never been thought of…rushed past the grand stand in sweeping triumph’.
See also: dark, horse
Farlex Partner Idioms Dictionary © Farlex 2017

a dark ˈhorse

(British English) a person who does not tell other people much about their life, and who surprises other people by having interesting qualities: You’re a dark horse! I had no idea you could play the piano so well.This phrase comes from horse racing. A dark horse was a horse that nobody knew much about and later came to mean somebody who wins a race unexpectedly.
See also: dark, horse
Farlex Partner Idioms Dictionary © Farlex 2017

dark horse, a

An unexpected potential winner. The term dates from the nineteenth century and comes from racing, where a horse is termed “dark” when its ancestry and history are unknown. It was so used by Benjamin Disraeli in his novel, The Young Duke (1831), but the precise origin is obscure. Some think it comes from the owner’s dyeing a horse’s hair to disguise it and so get better odds; others cite the practice of a particular American horse trader who made his fast black stallion look like an ordinary saddle horse, rode into town, set up a race, and consistently came out a winner. The term was soon transferred to political candidates on both sides of the Atlantic. The first American presidential dark horse was James Polk, who won the 1844 Democratic nomination only on the eighth ballot and went on to become president.
See also: dark
The Dictionary of Clichés by Christine Ammer Copyright © 2013 by Christine Ammer
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References in periodicals archive ?
Such a horse is called a dark horse, not because of its color, but because of its obscurity.
AT long last, after many months of searching, we have a dark horse for Euro 2000.