private domain name
A domain name used within a private network, not publicly registered in the global DNS.
Private domain names are used on the internal company network.
A general domain name, which can be public or private. 私設領域名 specifically refers to a private domain name not registered in the public DNS.
Compound of 私設 (private, privately established) + 領域 (area, domain) + 名 (name). A technical term likely coined in Japanese computing contexts.