dark
Preserved but no longer current.
"keep it DARK," i.e., secret. A DARK horse is, in racing phraseology, a horse of whom nothing positive is known, but who is generally supposed to have claims to the consideration of all interested, whether bookmakers or backers.
Era: ca. 1874 (Victorian)
Sources & notes
Historical definition reproduced from Hotten’s The Slang Dictionary (1874, public domain; Project Gutenberg #42108, retrieved 2026-07-31). Reflects the attitudes of its era.
Common questions
What does “dark” mean?
"keep it DARK," i.e., secret. A DARK horse is, in racing phraseology, a horse of whom nothing positive is known, but who is generally supposed to have claims to the consideration of all interested, whether bookmakers or backers.
Is “dark” formal or informal?
No register label has been reviewed yet — treat it as neutral and check the usage notes above.