The act of gripping the elastic band on the back of ones underwear, preferably a nerds, and pulling straight back to maximize length. You then precede to pull the underwear upwards and loop it over the nerds head, pulling his head back in a very painful manner.
(Noun) Dude, Billy totally just gave that nerd a Brazilian covered wagon!!!
(Verb) Dude, Billy totally just Brazilian covered wagoned that nerd!