n. What accumulates when slush, snow and/or dirt accumulate behind an automobile's tires and cling to the body of the vehicle. When conditions drop below freezing, the vehicle carries around these dirty clumps of slush.
"I've never seen such poor road maintenance. Look at the slush buggy behind each and every tire on my Honda."
"Let's see who can drive the longest in this snow and keep their slush buggies intact!"