Definition of life-or-death in US English:

life-or-death

adjective

  • That involves or is regarded as involving life and death; (by extension) extremely urgent or dangerous.

Origin

Mid 19th century; earliest use found in Dublin University Magazine. From life + or + death, after a matter of life or death.

Pronunciation

life-or-death

/lʌɪfɔːˈdɛθ/