lifeline; indispensable thing
Figurative use: something essential for survival, success, or well-being. Often used in phrases like 生命線を握る (hold the lifeline) or 生命線を断つ (cut off the lifeline).
This road is a lifeline for the disaster-stricken area.
He holds the company's lifeline.
life line (palm reading)
The line on the palm used in palmistry to indicate vitality and life span. Often discussed in fortune-telling contexts.
In palm reading, a long life line is said to indicate a long life.