What is a SHTF situation?

[Scythe13]

SHTF has to be something that is out of the normal, that has to be effecting,.. not your life, but the way you have to live your life from that point on, no matter what the emergency is,.. if at the end of the day everything returns to normal, then the s**t didnt hit the fan

I really agree with that. The only thing I would add, would be a timescale to the amount of time you have to live in the changed way.