You may find it interesting to know that in order for a contract to be legally binding, it needs a termination date and a beginning date.
When a contract reaches the termination date, it is said to have "expired".
Incidentally, there are a few other terms that might be of interest to you regarding listings.
1. Withdrawn - when a listing is withdrawn the owner of the home elects to remove the home from showing, however the listing contract is still in force. Realtors are prohited from soliciting the seller to re-list the property.
2. Hold - When a property is an active listing, it can be placed on HOLD, meaning it is temporarily off the market. Typcially this can be around the holidays, however it can be for any reason.
3. Cancelled - When a listing is cancelled it there is no contract between the listing agent and the seller and the listing is no longer available for showing.
Hope this is helpful.
If you have a home you are interested in - an agent can easily find out if the house is still "technically" on the market.