What is a SHTF situation?

[Highlander]

The phase SHTF is often over used, or used in the wrong text or at least it is for me,... I was inside the Belfast bus station when the bomb went off ....in 1969 was it?,.. yes I am that old,...there were bodies and body parts all over the place,... I didnt think that was the SHTF, it was just something that needed dealing with,...and was becomeing normal at around that time

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