I got a bit of chuckle over this recent definition from Urban Dictionary. (Bold added to the part I found especially amusing.)
1. A technically bankrupt company that is kept alive with large infusions of government money for the sake of “stability” in the U.S. financial system. 2. A large financial company with negative net worth that continues to operate, despite having no clear path to solvency. 3. The UnDead of Wall Street.