I didn't know what "nova" meant at first, but I've seen it enough in context to infer that it means "doing a ton of damage in a short period of time."
How was this term coined? How was it popularized?
EDIT: It looks like the term isn't as common as I first thought. It must just be in the communities I'm involved with (D&D). Essentially a nova-based PC is one that can expend a large amount of a limited resource all at once in an attempt to do massive amounts of damage. This would commonly be used when building an assassin type character.
I had guessed that the term was just metaphorically referring to a supernova, but it seemed to be used frequently enough that it may have a specific origin.