The full form of SHTF is shit hit the fan
The acronym “SHTF” represents the phrase “shit hit the fan” or “shit hits the fan.” This phrase is often interpreted to mean when something awful happens and chaos follows, such as a major natural disaster occurring and survivalist scenario.

Origin of SHTF
Although some information states that the phrase “shit hits the fan” or “shit hit the fan” dates back to the 1930s and originated in the military, the first known written record of the phrase that has solid proof occurred in 1948 in a novel by author Norman Mailer titled The Naked and the Dead. However, variations of the phrase were used in years before such as “stuff hits the fan.” Therefore, one can assume this phrase was in use well before it made an appearance in Mailer’s novel, but one cannot say for sure how long before. With the dawn of the internet and desire to make electronic communication much simpler, faster, and easier came acronyms to represent some of the more widely known phrases that have been used for years such as this one.

Other Meanings
There are no other meanings known presently.

Example Conversations
A text conversation between two friends.

Friend 1: Hey, you are a fan of The Walking Dead right?
Friend 2: Yes! Still watch it faithfully every Sunday night. Why?
Friend 1: I was just wondering what you would do if shtf like it did in that show?
Friend 2: Honestly, I can’t say one way or the other.