Individual or organization that performs the operations of a system.
Sources:
NIST SP 800-160v1r1
from
ISO/IEC/IEEE 15288:2015
An FCKMS role that is authorized to operate an FCKMS (e.g., initiate the FCKMS, monitor performance, and perform backups), as directed by the system administrator.
Sources:
NIST SP 800-152
under Operator