lifeline
noun
life·line ˈlīf-ˌlīn 
1
: a line (such as a rope) used for saving or preserving life: such as
a
: a line along the outer edge of the deck of a boat or ship
b
: a line used to keep contact with a person (such as a diver or astronaut) in a dangerous or potentially dangerous situation
2
: something regarded as indispensable for the maintaining or protection of life
Example Sentences
The river is the town's lifeline. The new jobs were an economic lifeline for a city in need of help. The radio was their lifeline to the outside world. They threw a lifeline to the man overboard.
Recent Examples on the Web China has been a lifeline for Russia amid mounting international sanctions, particularly as a destination for its energy exports; in recent months, Russia has been China’s top oil supplier. 
Jennifer Jett, NBC News, 15 Sep. 2022 Railroads are a lifeline for bulk commodities such as ethanol and coal. Paul Berger, WSJ, 14 Sep. 2022 Now the emergency aid programs have largely lapsed, ending what for some was a lifeline. Kurtis Lee, BostonGlobe.com, 10 Sep. 2022 The community's support has been a lifeline for Mark and Jaclyn since Jared's death, the couple said. Megan Myers, Fox News, 2 Sep. 2022 The water is a lifeline for northern desert cities including Tijuana and a large farm industry in the Mexicali Valley, just south of the border from California’s Imperial Valley. The Salt Lake Tribune, 16 Aug. 2022 The water is a lifeline for northern desert cities including Tijuana and a large farm industry in the Mexicali Valley, just south of the border from California’s Imperial Valley. Suman Naishadham And Sam Metz, Anchorage Daily News, 16 Aug. 2022 The water is a lifeline for northern desert cities including Tijuana and a large farm industry in the Mexicali Valley, just south of the border from California's Imperial Valley. CBS News, 16 Aug. 2022 These services could be a lifeline for families in states with bans on care and for people in more isolated, rural regions of the country. Dallas Ducar, Scientific American, 12 Aug. 2022 See More
Jennifer Jett, NBC News, 15 Sep. 2022 Railroads are a lifeline for bulk commodities such as ethanol and coal. Paul Berger, WSJ, 14 Sep. 2022 Now the emergency aid programs have largely lapsed, ending what for some was a lifeline. Kurtis Lee, BostonGlobe.com, 10 Sep. 2022 The community's support has been a lifeline for Mark and Jaclyn since Jared's death, the couple said. Megan Myers, Fox News, 2 Sep. 2022 The water is a lifeline for northern desert cities including Tijuana and a large farm industry in the Mexicali Valley, just south of the border from California’s Imperial Valley. The Salt Lake Tribune, 16 Aug. 2022 The water is a lifeline for northern desert cities including Tijuana and a large farm industry in the Mexicali Valley, just south of the border from California’s Imperial Valley. Suman Naishadham And Sam Metz, Anchorage Daily News, 16 Aug. 2022 The water is a lifeline for northern desert cities including Tijuana and a large farm industry in the Mexicali Valley, just south of the border from California's Imperial Valley. CBS News, 16 Aug. 2022 These services could be a lifeline for families in states with bans on care and for people in more isolated, rural regions of the country. Dallas Ducar, Scientific American, 12 Aug. 2022 See More Word History
First Known Use
1700, in the meaning defined at sense 1