A Subroc was a type of submarine launched rocket intended for use as an anti-submarine weapon. It was designed to be a similar in size and shape to a standard torpedo so that it could be fired from a submarine's torpedo tubes. On launch, the subroc rises to the surface, then ignites its solid fuel rocket engine and flies to its programmed destination. The warhead then separates and reenters the water before exploding in proximity to its target. When equipped with a nuclear warhead a direct hit is not necessary.
The principle Subroc used by the US Navy was the Goodyear UUM-44 Subroc. Developed in 1965, the Subroc was never used in anger and all were decommissioned following the end of the Cold War in 1989. Towards the end of the 1970s, a planned successor, the UUM-125 Sea Lance, was frequently delayed due to funding problems and eventually cancelled.
Subroc was not strictly an anti-submarine weapon: it was thought that the noisy alpha class submarine of the Soviet Union would serve as a beacon as to the location of a Soviet battle group, and a large-enough nuclear warhead would not only destroy the submarine, but all accompanying warships as well.