LIFELINE
lifeline
(noun) line thrown from a vessel that people can cling to in order to save themselves from drowning
lifeline
(noun) line that raises or lowers a deep-sea diver
lifeline
(noun) support that enables people to survive or to continue doing something (often by providing an essential connection); “the airlift provided a lifeline for Berlin”; “she offered me a lifeline in my time of grief”
Source: WordNet® 3.1
Etymology
Noun
lifeline (plural lifelines)
A line to which a drowning or falling victim may cling.
(by extension) A source of salvation in a crisis.
A means or route for transporting indispensable supplies.
(engineering) System or structure of vital importance to a community.
(nautical) On the deck of a boat, a line to which one can attach oneself to stay aboard on rough seas.
Synonym: jackstay
(diving) A line from the diver to a tender at the surface control point.
Synonym: tether
(palmistry) A particular crease in the palm.
Synonym: line of life
Source: Wiktionary