Profoundly offensive swear used to offend the recipient by insulting their father. Borders on fighting words
Jerald: shut up you’re a stupid motherfucker!
Bartholomew: what?
Jerald: you heard me stupid motherfucker!
Bartholomew: you’re calling me a stupid motherfucker because that’s all you can roll out of mouth like a retarded son of a shithead!