thunder pot

A large pot or chamber kept in the back of a station wagon or SUV that is used to urinate or defecate to avoid having to pull over to use the restroom.

Sarah used the Thunder Pot on the way the Shelly's wedding to take a huge dump so we didn't have to pull over to the rest stop.

Thunder Pot

verb: When you are on the toilet and you fart, and the bowl amplifies the sound of the fart.

I could hear Tom thunder pot all the way from the kitchen!