Organization or person that receives a product or service.
NIST SP 800-160 [Superseded]
The term customer applies to a person or organization who subscribes to a service offered by a telecommunications provider and is accountable for its use. A customer is permitted to use an NE to make calls and configure local line parameters (e.g., configure the numbers that should receive forwarded calls).
In some circumstances a customer can also play the role of administrator, for example, when the customer has access to operations information that would permit him to reconfigure his circuits. Some service providers offer this service, as well as other OAM&P features, to customers for a fee.
NIST SP 800-13 under Customer