a dark horse
Also found in: Dictionary.
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 who surprises others with their skills or talents. 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.
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.