Life-Or-Death Meaning

(idiomatic) Of critical importance to the success of a particular endeavor.

Example: 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.
  Obtaining financing was a life-or-death matter for the research.