Someone who is so not famous that this is where they have ended up
i.e Bobby Davro is a Z List celebrity
the section of your MSN messenger contact list used for people you don't really want to talk to, or you would generally ignore, but are too polite to delete. the category can be anything beginning with the letter 'Z', as it will then appear below all the other categories.
my Z list is almost as long as my friends section!