Nuclear latency is the condition of a country possessing the technology to quickly build nuclear weapon

Nuclear weapon

A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion. Both reactions release vast quantities of energy from relatively small amounts of matter. The first fission bomb test released the same amount...

s, without having actually yet done so. Because such latent capability is not proscribed by the Nuclear Non-Proliferation Treaty

Nuclear Non-Proliferation Treaty

The Treaty on the Non-Proliferation of Nuclear Weapons, commonly known as the Non-Proliferation Treaty or NPT, is a landmark international treaty whose objective is to prevent the spread of nuclear weapons and weapons technology, to promote cooperation in the peaceful uses of nuclear energy and to...

, as a work-around of the treaty this is sometimes called the "Japan Option", as Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

 is a clear case of a country with complete technical prowess to develop a nuclear weapon quickly.

This term has also been used to refer to the 1989 incident

Timeline of North Korea nuclear program

This Chronology of the North Korean Nuclear Program begins in 1989 with the end of the Cold War and the decline of the USSR as the main economic ally of North Korea...

in which North Korea began invalidating the Non-Proliferation Treaty.