One who achieves unexpected support and success as a political candidate, typically during a party's convention.(noun)
A little-known, unexpectedly successful entrant, as in a horserace.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "dark horse" in a sentence
"Curley’s old mouth pouted contemptuously as she considered them: John with his irascibility, his pomposity and his moments of sheer obstinacy; Paul lathering and shouting and making an exhibition of himself; and now the dark horse Mike, who had never really wanted anything before."