A humorous way of describing a really rough pooping incident. Most commonly used when one is A) severely constipated OR B) has explosive diarrhea. The meaning of the term comes from the need to light not one, but two matches (to cover the stench), and the fact that you broke out into a huge sweat, sometimes requiring the need to disrobe during the act of crapping.
Wow... That dump was a rough one... It ended up being a Two-Match Sweater!!