Glue Record
An IP address record served by a parent zone that breaks the chicken-and-egg problem when a domain's nameservers live inside the domain itself.
A glue record solves a bootstrap problem: if example.com's nameservers are ns1.example.com and ns2.example.com, a resolver cannot look up those names without first asking those very nameservers. The parent zone (here, .com) breaks the loop by serving the IP addresses of the in-bailiwick nameservers alongside the NS delegation. Without glue, the domain becomes unresolvable. Registrars expose glue records under names like "host records" or "private nameservers." Missing or stale glue (where the registrar's glue points to a different IP than the nameserver actually uses) is a classic cause of intermittent DNS failures.