Multi-purpose exclamation of surprise, dismay, congratulations; other forms include 'Shit my bitch', 'My bitch shit', 'Shit-bitch my', 'Shit in my bitching shit', 'Bitch in my shitting bitch-shit', etc.
Mary: 'Hey, I finally turned my cunt inside out...'
John: 'BITCH MY SHIT!'
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