Access to an organizational information system by a user (or an information system acting on behalf of a user) communicating through an external network (e.g., the Internet).
SOURCE: SP 800-53
Access by users (or information systems) communicating external to an information system security perimeter.
SOURCE: SP 800-18
The ability for an organization’s users to access its nonpublic computing resources from external locations other than the organization’s facilities.
SOURCE: SP 800-46
Access to an organization's nonpublic information system by an authorized user (or an information system) communicating through an external, non-organization-controlled network (e.g., the Internet).