lifeline

noun7

1. •
   A line to which a drowning or falling victim may cling.
2. •
   A source of salvation in a crisis.

   • The girls, of course, were my lifeline during this time. — 2012
3. •
   A means or route for transporting indispensable supplies.

   • Planners did not see the access routes as west Berlin's sole lifeline, which now seems instinctive to us. — 2012
4. •
   A system or structure of vital importance to a community.
5. •
   On the deck of a boat, a line to which one can attach oneself to stay aboard on rough seas.
6. •
   A line from the diver to a tender at the surface control point.
7. •
   A particular crease in the palm.