Sudden onset shit. When the urge to poops hits you out of nowhere and you can't delay any longer. A way to casually tell someone you have to shit without everyone know you have the diarrheas.
1. Save Our Souls, a distress signal often used by ships at sea.
2. The vulgar definition of this is Sack of Shit.
1. We've been hit by a torpedo! Send an S.O.S.!
2. John: Yeah my boss made me stay four hours after clock out just to talk about his cat and I ended up getting home at 9pm; what a SOS.