'life-sustaining' definitions:

Definition of 'life-sustaining'

(from WordNet)
adjective
Performing an essential function in the living body; "vital organs"; "blood and other vital fluids"; "the loss of vital heat in shock"; "a vital spot"; "life-giving love and praise" [syn: vital, life-sustaining]

Definition of 'life-sustaining'

From: GCIDE
  • life-sustaining \life-sustaining\ adj. being the seat or source of life; performing a necessary function in the living body; as, the need for life-sustaining air and water.
  • Syn: vital. [WordNet 1.5 +PJC]