the directory on a unix or linux box which stores passwords. on various servers the passwords are either encrypted in an algorithm or shadowed with a "*" or "x" symbol.
The password that you use for every website, email account, facebook, twitter, everything. Having a 'life password' is not a good idea, but everyone does it.
My friend found out my life password and wrecked my facebook account, stole all my paypal money and emailed offensive images to my mother.