- life or death
- Of critical importance to the survival of a living organism.
- Good camoflouge is life-of-death for many animals in the wild.
- Having death as a possible or even likely outcome; perilous.
- Ascending Mount Everest can be life-or-death for an inexperienced climber.
- (idiomatic) Of critical importance to the success of a particular endeavor.
- Obtaining financing was a life-or-death matter for the research.