upset stomach Posted in U Best definition upset stomach (Honestly? No one has defined this yet?) When you feel pain or discomfort in your stomach due to overindulgence or something like that. “Jeez, after that entire pizza I got an upset stomach to deal with!” How satisfied are you with the definition? Looking for upset stomach meaning? Delighted that you discovered the greatest determine on our web site! Recently this definition was actually observed 49 times.