1 a an annual horse-race run on the flat at Epsom. b a similar race elsewhere (Kentucky Derby).
2 any important sporting contest.
3 (derby) US a bowler hat.
Phrases and idioms:
Derby Day the day on which the Derby is run. local Derby a match between two teams from the same district.
Etymology: the 12th Earl of Derby d. 1834, founder of the horse-race
Useful english dictionary. 2012.