You've just been hit in the belly, you are bending over, can't continue to stand. Down to your knees or even worse curling into a fetal position hugging your belly. Solar plexus can do that but this was right on top your bellybutton or maybe just below. Bad if this was one of the first punches to your belly. Even worse if in the first moments of a fight. Who has felt this? How did you feel? Or maybe you did this to someone?