the explosive/burning diarrhea you experience after eating large quantities of spicy food, eg. - mexican food
GUY 1 - "man i had the worst fierrhea last night...to much mexican food"
GUY 2 - "dude what the hell is fierrhea?"
GUY 1 - "its basicly like shitting lava...diarrhea that burns like hell on the way out..it sucks"
GUY 2 - "hahaha dude thats fuckin epic....nasty as hell though"
When one's ass is on fire due to eplosive diarrhea usually taking place the morning after an extremley spicy meal.
Those chicken wings gave me fierrhea so bad my husband could hear me screaming downstairs. "Oh fuck! My ass-hole is on fire!"