Definition of Life support

Life support: 1. A therapy or device designed to preserve someone's life when an essential bodily system is not doing so. Life support may, for example, involve enteric feeding (by a tube), total parenteral nutrition, mechanical ventilation, a pacemaker, defibrillator, heart/lung machine, or dialysis.
2. Something that sustains life, as in "The earth is the ultimate life support system."
3. A product, program or company being propped up, as in "Medicare is on life support."