millenarianism in British English
(ˌmɪlɪˈnɛərɪəˌnɪzəm), millenarism (ˈmɪlɪnəˌrɪzəm), millennialism (mɪˈlɛnɪəˌlɪzəm) or millennianism (mɪˈlɛnɪəˌnɪzəm)
noun1. Christianity the belief in a future millennium following the Second Coming of Christ during which He will reign on earth in peace: based on Revelation 20:1–5
2. any belief in a future period of ideal peace and happiness