It's when a bunch of Hispanic or Latino gang members from the South Coast shit in a pan or bowl, put a cherry on it, and make a white guy eat it. The name relates to the fact that there are lots of soft serve ice cream shops on the southcoast - Since most shit tends to be soft, the bowl of feces is meant to look like a chocolate ice cream sundae with a cherry on top. Whatever guy is beatdown, pawned or owned, then gets it "served" to them as the Coup De Grace. Made famous in the city of New Bedford, MA.
Seamus was disrespecting the crew, so we gave him a helping of SouthCoast Soft Serve, and now he doesn't talk shit anymore!