n
1 (nautical 海)
(a) line or rope for saving life such as that attached to a lifebelt, or fastened along the deck of a ship in a storm for sailors to hold on to 救生索.
(b) line attached to a deep-sea diver （深海潜水员的）信号绳.
2 (fig 比喻) anything on which sb/sth depends for continued existence 生命线; 命脉
*Public transport is a lifeline for many rural communities. 公共交通对许多农村居民来说是不可或缺的.

n[C]
something which someone depends on completely
lifeline 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.
a rope used for saving people in danger, especially at sea