Dual use goods are products and technologies normally used for civilian purposes but which may have military applications.
In politics and diplomacy, dual-use is technology that can be used for both peaceful and military aims.
More generally speaking, dual-use can also refer to any technology which can satisfy more than one goal at any given time. Thus, expensive technologies which would otherwise only serve military purposes can also be used to benefit civilian commercial interests when not otherwise engaged such as the Global Positioning System.
Originally developed as weapons during the Cold War, the United States and the Soviet Union spent billions of dollars developing rocket technology which could carry humans into space (and even eventually to the moon). The development of this peaceful rocket technology paralleled the development of intercontinental ballistic missile technology and was a way of demonstrating to the other side the potential of one's own rockets.
Those who seek to develop ballistic missiles may claim that their rockets are for peaceful purposes, e.g., are for commercial satellite launching or scientific purposes. However even genuinely peaceful rockets may be converted into weapons, and provide the technological base to do so.
Within peaceful rocket programs different peaceful applications can be seen as having parallel military ones for example the return of scientific payloads safely to earth from orbit would be indicative of a re-entry vehicle capability and the demonstration of the ability to launch multiple satellites with a single launch vehicle can be seen in a military context as having the potential to deploy multiple independently targetable reentry vehicles.
Dual-use technology refers to the possibility of military use of civilian nuclear power technology. Many technologies and materials associated with the creation of a nuclear power program have a dual-use capability, in that several stages of the nuclear fuel cycle allow diversion of nuclear materials for nuclear weapons. When this happens a nuclear power program can become a route leading to the atomic bomb or a public annex to a secret bomb program. The crisis over Iran’s nuclear activities is a case in point.