a non-functioning domain - this means your web address will not work, and any emails sent to that address will not work
Used to mean two very different things, either: (a) an on-hold domain or (b) an available domain.
a domain where the last owner has let the registration expire. Many webmasters try to grab expired domains that already have links pointing to them to have new sites rank better in the search engines. Some webmasters will try to use this trick as a way to get legitimate links and referral traffic to sites containing adult content.
A domain that has not been reregistered by the owner in the grace period allotted eventually becomes expired, or unusable by the owner, and is placed into the pool of available names again.
domain name whose renewal date has passed, but which has not yet been dropped from the domain name system.
Previously registered domain names that have not been re-registered or renewed for a new term. At this point the name begins the "drop cycle" and may take quit some time to be released back to the public.