Nova

In GEB, the term Nova references the huge Aragami, nurtured by Johannes von Schicksal, that is said to be capable of devouring the entire world in an event known as the Devouring Apocalypse.

Trivia
Scientifically, a Nova is thermonuclear explosion that happens in the event that a white Dwarf star accumulates excessive amounts of hidrogen in its surface, because of having a nearby evolved star.