1) Everyday German physics term 2) Familiar German physics term 3) German physics term 4) Prevalent German physics term 
literally "ball lightning", fireball.
[astrophysics] In theoretical physics, a kugelblitz (German: `ball lightning`, not to be confused with ball lightning) is a concentration of light so intense that it forms an event horizon and becomes self-trapped: according to general relativity, if enough radiation is aimed into a region, the concentration of energy can warp spacetime eno...