What does 'Survivor Car' Mean?

I see the term 'survivor car' in ads and have been trying to figure out what it really means. The associated car descriptions seem to vary wildly as to originality and condition, so I am wondering if this is just used to trick potential buyers into thinking they are getting something special, or does it actaully have a certain definition? (Like the term 'original' has a specific meaning.). Any inputs/info/opinions are welcomed.