The person, company or entity who owns or holds a domain name. When corporations and companies register a domain name, the registrant should be the company name (not an individual employee within the company) to ensure the business maintains ownership of the domain name.
See “Registering a Domain Name” and “Understanding Internet Governance” in the Did You Know…? section of Webopedia.
See also “Countries and Their Domain Extensions” in Webopedia’s Quick Reference Section.