A black hole bomb is the name given to a physical effect utilizing how a bosonic field impinging on a rotating black hole can be amplified through superradiant scattering. If the amplified field is reflected back towards the black hole, the amplification can be repeated, leading to a run-away growth of the field, i.e. an explosion. This explosion can be as powerful as a supernova. One way this reflection could be realized in nature is if the bosonic field has mass. The mass of the field can then cause the amplified modes to be trapped around the black hole, leading to an endless cycle of self-amplification. The mechanism by which the black hole bomb functions is called superradiant instability. It can also refer to one such method of creating such a runaway effect, a Penrose sphere with no means for energy to passively escape.