A nuclear missile whose rocket booster cannot be detected by enemy military satellites.
In 1964, the Soviet GRU became the first to begin development of stealth nukes. They devised a synthetic range extension system, in which the Shagohod accelerates to 300 miles per hour using a rocket booster and then directly launches an IRBM (intermediate range ballistic missile).
In 2005, the CIA, the US Army, and ArmsTech achieved stealth nuke capability with Metal Gear REX. REX would use a rail gun to deliver the nuclear payload to the target without burning any propellant, while also avoiding detecting by enemy radar.