Definition of Newcastle
1an industrial city in northeastern England, a port on the Tyne River; population 170,200 (est. 2009). Full name Newcastle upon Tyne. 2an industrial town in west central England, southwest of Stoke-on-Trent; population 77,500 (est. 2009). Full name Newcastle-under-Lyme. 3an industrial port on the southeastern coast of Australia, in New South Wales; population 152,659 (2008).