An urban brownie is when you have to take a dump and your only option for excrement is a public restroom. A technique, developed by the Dutch in the late 1800's, known as "hovering" is one way of coping with an urban brownie. This involves using your hamstrings to avoid making contact with the seat of the toilet.
Warning: Enlarged and strengthened hamstring muscles may visually skew observed penis size in a negative manner. Hover in moderation.
"Oh man, I hate the airport. I'm about to drop an urban brownie too."