Fizzy Bum Gravy - A result of eating mystery dishes and strange foreign foodstuffs, or from inadvertently drinking the local water on foreign land. The next day, said concoction plays havoc with your intestines to the point that any loud noises or sudden movements will make you shit yourself. The resultant explosion from your arse sounds like the last of a washing up liquid bottle, emptying the entire contents of your bowel in 3 seconds. The by-product of this experience is known as FBG.
Oh, I can feel an FBG coming on!
Oh, I have a terrible case of the FBGs.
My guts are in turmoil; this next trip to the shitter is definitely going to be an FBG event.