fireball

n. 1. (Mil.) A ball filled with powder or other combustibles, intended to be thrown among enemies, and to injure by explosion; also, to set fire to their works and light them up, so that movements may be seen. [ 1913 Webster ]

2. A rare phenomenon often associated with or caused by lightning, resembling a luminous ball of fire passing rapidly through the air or along solid objects, then disappearing, and sometimes exploding. It seldom lasts more than a few seconds. Also called ball lightning, globe lightning, globular lightning, or kugelblitz. [ Webster 1913 Suppl. +PJC ]

3. A large mass of fire caused by a large explosion, as of inflammable liquids or a nuclear device. The larger fireballs, as of nuclear explosions, rise seemingly intact into the air and may reach high altitudes while still glowing. [ PJC ]