What term refers to a sustained service interruption?

The term that refers to a sustained service interruption is "outage." In the context of utility services, an outage typically indicates that there is a significant and ongoing failure in the provision of service, such as the loss of electricity, water, or telecommunications. This term reflects the idea of a complete loss of functionality or availability across an area or system for a prolonged period, which is often the result of infrastructural issues, maintenance, or unforeseen events.

In contrast, a "fault" generally refers to a defect or failure in the system that can lead to an outage, but it doesn't inherently describe the duration or the totality of the interruption. A "surge" typically describes a sudden increase in power or voltage, which may lead to damage but is not related to a sustained loss of service. "Disruption" can imply a break in normal operations, but it doesn’t always denote a complete service interruption that lasts for a significant time. Thus, "outage" is the precise term for a sustained and complete interruption of service.