n. A nation that has vastly greater economic, political, or military power than any other nation.
2001
Long the principal superpower and now the single superpower — or a "hyper-power," in the favoured phrase of the French — the U.S. is the contemporary Rome. Its power, much of it invisible because it's based on culture or technology rather than just upon smart bombs and cruise missiles, reduces the power of all others, whether the European Union or China or Russia, let alone Canada, to the third rank, sort of like Gaul's status at the height of the Roman Empire.
1991 (earliest)
The result is that the United States now appears as a world power hors de pair. Its superiority in politico-military power over the Soviet Union leaps to the eye and seems to have impressed even the Red Army generals. It is the one country in the world that has the ability to fight a large-scale high-technology war. This is a gap that can only increase as President Gorbachev struggles with growing economic collapse and political disintegration at home. There are now no longer two superpowers. There is one hyper-power with all the rest far behind.
This word — an extreme version of the older term superpower (1930) — was popularized by French foreign minister Hubert Vedrine, who in 1998 said "There is one hyper-power and seven powers with world influence — Russia, China, Japan, India, France, Germany and Britain." However, as the earliest citation shows, the term is a few years older than that.