fireball

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A brilliantly burning sphere.
• noun A highly luminous, intensely hot spherical cloud of dust, gas, and vapor generated by a nuclear explosion.

from The Century Dictionary.

• noun A ball of fire, as the sun.
• noun Milit., a ball filled with explosives or combustibles, intended to be thrown among enemies, to injure them by explosion, to set fire to their works and expose their movements, or simply to produce the last result by the light of its own combustion.
• noun Globe-lightning; an electrical phenomenon sometimes seen in thunder-storms, having the appearance of a globe of fire falling from the clouds and often bursting with a loud report.
• noun A ball composed of very fine anthracite coal or dust and clay, used to kindle fires.
• noun The scarlet lychnis, Lychnis Chalcedonica.
• noun In heraldry, same as ball fired (which see, under ball): as, a fire-ball fired in four places.

from the GNU version of the Collaborative International Dictionary of English.

• noun (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.
• noun 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.
• noun 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.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A ball of fire.
• noun An explosion, which results in a fireball.
• noun astronomy A meteor bright enough to cast shadows.
• noun A class of sailing dinghy with a single trapeze and a symmetrical spinnaker, sailed by a crew of two.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the luminous center of a nuclear explosion
• noun an especially luminous meteor (sometimes exploding)
• noun a highly energetic and indefatigable person
• noun a ball of fire (such as the sun or a ball-shaped discharge of lightning)