WordNet (r) 3.0 (2006):

life support
    n 1: equipment that makes life possible in otherwise deadly
         environmental conditions; "the astronauts relied on their
         life-support systems" [syn: life-support system, life
         support]
    2: medical equipment that assists or replaces important bodily
       functions and so enables a patient to live who otherwise
       might not survive; "the patient is on life support" [syn:
       life-support system, life support]