Stomach Dishwasher

I've had many weird and awkward conversations with people, but never has one come up like this;  I was talking to a kid when he said that he just did a dishwasher imitation.... I was trying to figure out how that was at all possible.  I told my sister and we tried a number of different sounds and movements, but we just couldn't get one that was even close to a dishwasher.  Then she starts going off about somehow if your head was in your stomach it might work.. What????????