Fireball \Fire"ball`\, n. Ball, or globular, lightning.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Fireball \Fire"ball`\, n.
   (a) (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.
   (b) A luminous meteor, resembling a ball of fire passing rapidly through the air, and sometimes exploding.

Source: Webster's Revised Unabridged Dictionary (1913)