mega-rrhea Share definition Flag diarrhea that is so powerful, explosive, and often times painful that it breaks all normal standards of fecal expulsion. "I drank 30-pack of beast ice last night and boy do I have mega-rrhea" mega-rrhea by jenn December 10, 2004 0 0 Get merch Get the mega-rrhea mug. Buy Now — $32.95 See more merch