Expression to describe when a person or activity has run its course and met its end. Dead. Finished. Done. The expression is thought to have originated from military pilots when reporting from the air the visual status of other planes that had gone down and met their end, and in doing so on the way down or at their final resting place (or both), were often times "upside down" with their wheels pointing up rather than down as they operationally should have been. When seen from high above upside down with belly and wheels pointing up, they were described as they appeared....."tits up".
Hey...are the Cowboys going to the Superbowl or not?
What? No man....they lost last Sunday. It's over. They're tits up dude.