a felt hat that is round and hard with a narrow brim
"The old gentleman adjusted his stiff derby as he walked into the crowded train station."
Any of several annual horse races.
"The local farmer brought a wheel of creamy derby to the market stall."
A type of cheese made in Derby, England.
In plain English: A derby is an exciting competition between two teams, often played in sports like baseball, horse racing, or basketball where each side represents different cities or regions.
"The local team won their first derby match in years against their rival neighbors."
A city and unitary authority in Derbyshire, in the East Midlands, England; formerly the county town.
"The historic cathedral stands proudly in the centre of Derby, serving as a landmark for the city and former county town."
The word derby comes from the famous Epsom horse race, which was named after Edward Smith-Stanley, the 12th Earl of Derby. This term entered English usage to describe both the specific sporting event and later the distinctive hat associated with it.