Stiff Shit commonly used in conjunction or in replacement of too bad. Used when someone is complaining of something or being a little bitch about a situation.
Example 1:
Boss: Mate I need you to start work a bit earlier tomorrow to get this job complete.
Employee: Oh but boss I really was looking forward to a sleep in tomorrow morning.
A metaphor: Taking a crap and then having to pull the poop out of the toilet and stuff it back into your butt.
After six months of work on this project, my boss signed off on it. Now its two weeks later and we find out that we were working off the wrong specification. So now I've got to go stuff shit back into my ass.
When an individual has to shit very badly and goes in his pants. What other people see is a reverse boner made of shit protruding from your back pocket.
Everyone has come across a shit sniff, it is the sound men make to inform other men in a public restroom that they are currently in the process of dropping a deep sea bog diver. It is simply a very short and abrupt sniff, it is clear that because of it's short duration a shit sniff is not used for the pleasure of sniffing shit, it is merely a warnig to others that the process is occuring.
Next time you are in a public toilet (and i know that sounds weird) have a listen and eventually you will hear a shit sniff but you do not mention it when you are in there you'll put them off their stroke.