A person you can always depend on to help you in a really messed up situation where you need a quick excuse/escape.
This person will always have that six sense to lie in favor of you when asked about your current location (sometimes without you giving them any real hint about it).
This person also happens to be in the right place at the right time when you're in trouble.
"Dude, that blind date is horrific! I need to call my lifeline."
"Thanks, man! You're a lifeline!"
In situations where you're running late getting into work:
Boss: "Do you know if your name came into work today?"
Lifeline: "Uh... Yeah, he came in an hour before I went on lunch break. He's somewhere around here."
A person who talks and talks and talks and talks (seemingly without the need to take breathes) and kills everyone's ears.
Typically, if you're talking about something that they are extremely interested in then they will talk circles around you.
Person 1: "And then Becky said that Lisa said that she liked me but she didn't really like me like talking about it, but she liked as in if we were trapped on a desert island I would have a chance, but only if I were the only person on the island I MEAN if I were the only male person on the island and she was on the island I would have a chance because she would give me a chance because I am a guy and she's..."
Person 2: "Whoa! Whoa! Whoa! Slow down, Rambo!"
Person: "Jeez! Rambo over there won't stop talking for s**t!"