A death march project is one for which an unbiased, objective risk assessment (which includes an assessment of technical risks, personnel risks, legal risks, political risks, etc.) determines that the likelihood of failure is >= 50 percent.
The risks are high but so are the rewards
[...] Ultimately, this is a personal choice, based on personal values; I'm no position to tell to anyone else what's right or wrong. I should emphasize, though, that I'm not as negative as one might think from the comments above. Though I'm much less naive than I was when I entered the computer world in the mid-1960s, I'm still attracted by entrepreneurial opportunities. Show me a sufficiently exciting risk/reward formula, and I'll sing up for yet another death march ...
The "Mt. Everest" syndrome
Why do people climb dangerous peaks like Mt. Everest, despite the pain and the risk? Why do people run a marathon and drive themselves to the point of physical collapse? Because of the challenge. [...]