The not so ingenious way of saying Shit and Fuck together. However, it is not considered a swear , so it is OK in public, if you put more emphasis on SHI than FUCK! It can be a Safe For Work shitplitive.
When a person is extremely distraut, confused, beaten or just generally pissed at a person or event. Or has a face to face run in with the cops or Chuck Norris.