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