Definition of "lifeline"

lifeline

/ˈlaɪfˌlaɪn/

noun
plural lifelines
1. A line to which a drowning or falling victim may cling.
2. (by extension) A source of salvation in a crisis.
  Quotations
  The girls, of course, were my lifeline during this time.
  2012, Melissa Rycroft, My Reality, Simon and Schuster
  Slowly I began to fill up some of the emptiness inside—writing had become my lifeline.
  2012, Aaron Dixon, My People Are Rising, Haymarket Books, page 64
3. A means or route for transporting indispensable supplies.
  Quotations
  Planners did not see the access routes as west Berlin's sole lifeline, which now seems instinctive to us.
  2012, Daniel F. Harrington, Berlin on the Brink, University Press of Kentucky, page 9
  It is no real surprise that half the UK's stations and 5,000 miles of route were recommended to close. Nevertheless, some great mistakes were made in Marples' devil-may-care purge that left commuters stranded and seaside resorts without a lifeline.
  2023 March 8, Howard Johnston, “Was Marples the real railway wrecker?”, in RAIL, number 978, page 50
4. (engineering) System or structure of vital importance to a community.
5. (nautical) On the deck of a boat, a line to which one can attach oneself to stay aboard on rough seas.
6. (underwater diving) A line from the diver to a tender at the surface control point.
7. (palmistry) A particular crease in the palm.