Originally an allusion to an unknown horse with a dark coat winning a race, as used in the 1831 novel The Young Duke by Benjamin Disraeli (1804–1881): “ […] and a dark horse, which had never been thought of, […] rushed past the grand stand in sweeping triumph.”
- (idiomatic) Someone who possesses talents or favorable characteristics that are not known or expected by others.
- (idiomatic, politics) A candidate for an election who is nominated unexpectedly, without previously having been discussed or considered as a likely choice.
- (horse racing) A horse whose capabilities are not known.
- Used other than with a figurative or idiomatic meaning: see dark, horse.
- The translations below need to be checked and inserted above into the appropriate translation tables, removing any numbers. Numbers do not necessarily match those in definitions. See instructions at Wiktionary:Entry layout#Translations.