when exiting the rear of a partner, a foamy brown solution immediately follows: resembling that of a rootbeer float.
"I was expecting soething bad to come out of your ass after that, but that was the chunkiest butt soda I have ever ingested.... I love you, Can we put on my A-Team dvd.
by Andy, Jeremy June 01, 2007
someone who spoils a good time with their own brand of douchery.
"Robert is being a butt soda."
by Chase December 24, 2003