From Longman Dictionary of Contemporary Englishlifelinelife‧line /ˈlaɪflaɪn/ noun [countable] 1 DEPEND/IT DEPENDSsomething which someone depends on completelylifeline to The telephone is her lifeline to the rest of the world.lifeline for The organization has proved to be a lifeline for thousands of needy families.2 TTWa rope used for saving people in danger, especially at sea
Examples from the Corpus
lifeline• These are isolated places dependent for a lifeline on the road from Shiel Bridge and otherwise quite inaccessible overland by vehicles.• Because I work at home, the telephone is like a lifeline to me.• The older philosopher offers the young Nietzsche a lifeline between his scholarly avocation and the world outside.• In the months ahead that link would prove a lifeline.• His shock decision - on the eve of Labour's party conference - threw a lifeline to battered Premier John Major.• The gaps in the Wall are the lifelines which sustain the régimes of the East and their ability to keep us divided.From Longman Business Dictionarylifelinelife‧line /ˈlaɪflaɪn/ noun [countable] something a country, organization etc depends on completelyHawaii has always been able to count on tourism, itseconomic lifeline. 