What is the meaning of Lifeline?

A line to which a drowning or falling victim may cling.

A source of salvation in a crisis.

A means or route for transporting indispensable supplies.

A system or structure of vital importance to a community.

On the deck of a boat, a line to which one can attach oneself to stay aboard on rough seas.

A line from the diver to a tender at the surface control point.

A particular crease in the palm.

Source: wiktionary.org