life-or-death

adjective

1. 1

   Of critical importance to the survival of a living organism.

   “Good camoflouge is life or death for many animals in the wild.”

2. 2

   Having death as a possible or even likely outcome; perilous.

   “Ascending Mount Everest can be life or death for an inexperienced climber.”

3. 3

   Of critical importance to the success of a particular endeavor.

   “Obtaining financing was a life-or-death matter for the research.”