The act of simultaneously of giving a blowjob to one person while taking a shit on someone else, while being shot up with heroin. Can be done with 3 people, but better with 4.

Fun fact: While this is all legal in San Fransisco, chewing tobacco is not.
Dude, did you see those those 4 homeless guys doing the San Francisco Sourdough on the corner back there?
by 2TiredMinds October 20, 2019
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Where one man curls up like a ball of dough while another man tries to put a bun in the oven.
"Bob the baker regularly gave special customers his own San Francisco Sourdough."
by StrokeTheDolphin July 24, 2021
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