A combination of "shit" and "terrific" used as an adjective to describe something something particularly bad, in a mildly sarcastic tone. Usually in response to a question of quality.
Clueless boyfriend who broke up with girlfriend the day before and calls her: "How are you?"
Crazed post-break up girlfriend: "Fucking shitterrific, hunny! Thanks for asking you cock-sucking fuckhead!"