superpower

superpower
/ˈsu:pəpauə(r); also, in ɑritish use, 英式英语读作 ˈsju:-; ˌsupɚ`paʊɚ/ n
any of the most powerful nations in the world, esp the USA or former USSR 超级大国
    [attrib 作定语]
a superpower summit 超级大国最高级会议.

牛津英汉双解词典