"STAR21" was the name given to the Class 952/953 (952・953形) 9-car experimental Shinkansen train developed in 1992 by the East Japan Railway Company in Japan to test technology to be incorporated in next-generation shinkansen trains operating at speeds of 350 km/h (217 mph) or higher. The name was an acronym for "Superior Train for the Advanced Railway toward the 21st Century".
Read article on Wikipedia