An emphatic interjection made when an off-handed sinister or perverse remark, often involving one's mom, leads to a cascade of incremental sarcastic wit that terminates with someone taking it way too far and getting graphically specific. The other participant in this cascade is left speechless, with the exception of the phrase: "Jesus Bob."
Paul: "...that's what she said."
Bob: "Who, you're mom? Yeah she says that to me all the time."
Paul: "Well the only words I get from your mom are groans."
Bob: "Well I fisted your mom in the ass while your dad asphyxiated himself in a gimp suit and jacked off!"
Paul: "Jesus Bob...."