Back-Order
A back-order, also referred to as a domain backorder, refers to the process of placing an order to register a domain name once it has expired and is in the process of being dropped from its current registrar.
Users wishing to backorder a domain name must use a service that specializes in domain back-orders (although there are some registrars who provide backorder services for domain names that it manages). These services generally charge a flat fee or, in the event that there is more than one potential buyer, they sell in an auction format. By using a backorder service, users increase their chances of registering the domain before others are able to do so.