Short for Doggie Style Only. Used to refer to women who from the rear view look extremelyattractive, but the front view looks more like she's ran into the back of a truck.
Generally used as a secret men's business tool, when one male only has a rear view and the other has seen the front...
It is the condition that men have, and the reason that they get so angry and aggressive. They need to release themselves and when they don't get any booty they suffer from DSO syndrome.