The quivers that start when you have a really huge shit on deck, and you've been holding it in for way too long. Shitvers usually result in explosive diarrhea and/or soiled britches.
1. When I got the shitvers at the beginning of the date, I knew it wasn't going to end well.
2. Karen: "Did you just get the chills?"
Bill: "No, that was the shitvers. There were no empty port-o-johns at the concert and I had to hold it. We need to stop at a gas station, fast, or I'm going to unload in your passenger seat..."