A sports-car race over approximately one thousand miles of roads in Italy, which was held annually 1927–41 and 1946–57. In later use: any of several similar events (some over shorter distances), especially an annual vintage-car event.
1930s; earliest use found in Barré Lyndon (1896–1972). From Italian Mille Miglia, lit. ‘a thousand miles’ from mille thousand (from classical Latin mīlle see milli-) + miglia, plural of miglio.