In physics, the minimum amount of fissionable material

required to sustain a chain reaction. Of a software product,

describes a condition of the software such that fixing one bug

introduces one plus epsilon bugs. (This malady has many

causes: creeping featurism, ports to too many disparate

environments, poor initial design, etc.) When software

achieves critical mass, it can never be fixed; it can only be

discarded and rewritten.