4d316111_ing_Kerberos__Support____Cisco_Table_1_Kerberos_Terminology_Definition
[Term] Kerberos realm [Definition] 
A domain consisting of users, hosts, and network services that are registered to a Kerberos server. The Kerberos server is trusted to verify the identity of a user or network service to another user or network service. Kerberos realms must always be in uppercase characters.
User Security Configuration Guide, Cisco IOS XE Release 3S - Configuring Kerberos [Support] - Cisco