n. (pl. -ies) 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. Derby Day the day on which the Derby is run. local Derby a match between two teams from the same district.
[ the 12th Earl of Derby d. 1834, founder of the horse-race ]