Pronunciation: (fīur'bôl"),[key] —n. 1. a ball of fire, as the sun; a shooting star.
2. a luminous meteor, sometimes exploding.
3. lightning having the appearance of a globe of fire; ball lightning.
4. the highly luminous central portion of a nuclear explosion.
5. a ball filled with explosive or combustible material, used as a projectile to injure the enemy by explosion or to set fire to their works.
6. Informal.an exceptionally energetic or ambitious person.