derby UK /ˈdɑː.bi/US /ˈdɝ.bi/ noun5 •Any of several annual horse races. •A sports match between rival teams. •A local derby.Defeat sees Forest remain a point outside the top six with a derby against Leicester up next. — 2011 •Any organized race. •(US) A bowler hat.He began to fan her with his hat. That was successful, for he struck her nose with the brim of his derby and she opened her eyes. — 1906 formsderbies