noun - A lifeline is a rope or line used for life-saving, typically thrown to rescue someone in difficulty in water or in mountain rescue scenarios.

noun - A lifeline also refers to a source of help or support that is relied upon in times of crisis or emergency.

noun - In the game show 'Who Wants to Be a Millionaire', a lifeline is a help or hint option that can be used when a contestant is unsure of an answer.