This article deals with Nuclear device as it relates to NationStates. For more general information, see the Wikipedia article on this subject.
In NationStates, the term nuclear device dominantly refers to a fission or fusion bomb, with a payload typically in the half kiloton to hundred megaton yield range. When used by a new nation or a nation that has not justified having a nuclear program, they are also known as n00ks. A good guide to the subject can be found [here].