1. Looking at voting system reliability, a failure is an event that results in: loss of one or more functions, degradation of performance resulting in a device that is unable to perform its intended function for longer than 10 seconds, automatic reset, restart, or reboot of the voting device, operating system or application software, requiring an unanticipated intervention by a person in the role of election worker or technician before normal operation can continue, or error messages or audit log entries indicating that a failure has occurred.

Source: Election Terminology Glossary - Draft, National Institute of Standards and Technology (NIST),

2. The inability of a system or component to perform its required functions within specified performance requirements.

Source: Information Technology Terminology, U.S. Election Assistance Commission,; Explore Terms: A Glossary of Common Cybersecurity Terminology, National Initiative for Cybersecurity Careers and Studies (NICCS),