What Does Domain Name Registrant Mean?
A domain name registrant is the person or entity that holds the right to use a specific domain name. The registrant can either be a person or an organization who is the domain license holder, legally bound by the domain's terms-of-service agreements.
Essentially, the registrant is the owner of the domain name of a particular website, but may not be the actual owner/administrator of the website, as there are cases where the domain name is only being leased to the website by the domain name registrant.
Techopedia Explains Domain Name Registrant
The domain name registrant is the legal owner of the domain name in the same essence that a person legally owns a car or real estate property. The registrant will receive all the billing as well as the administrative and technical notices associated with the registered domain name.
For example, if Mr. Joe Somebody registers a domain name called "joesbarbershop.com" then Mr. Joe Somebody is the domain name registrant of that particular domain name and will answer to all concerns regarding that domain name.