(the Derby) a flat race for three-year-old horses held annually at Epsom in England
a usu informal race or contest for a specified category of contestant
a donkey derby
a sporting match against a major local rival
chiefly NAmer a bowler hat
[named after Edward Stanley, twelfth Earl of Derby d.1834, who founded the horse race in 1780; (sense 4) said to be because bowler hats were worn at the Epsom Derby]