Costa Mesa (kŏsˈtə māˈsə) [key], city (1990 pop. 96,357), Orange co., S Calif., on the Pacific south of Santa Ana; inc. 1953. It is a transportation, residential, and light industrial center. In addition to research laboratories, huge corporate complexes and shopping malls like the South Coast Plaza have been built since the 1980s, and the city has two concert halls, one (2006) designed by César Pelli. Vanguard Univ. of Southern California is in Costa Mesa.