fatal error

critical mistake, fateful error, decisive error, deadly or lethal mistake

In computing, a fatal error is an error which causes a program to abort - and thus may return the user to the operating system. When this happens, data that the program was processing may be lost. A fatal error occurs typically in any of these cases:An illegal instruction has been attemptedInvalid data or code has been accessedThe privilege level of an operation is invalidA program attempts to divide by zero. (Only for integers; with the IEEE floating point standard, this creates an infinity instead)
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<programming, operating system> Any error which causes abrupt termination of the program. The program may be terminated either by itself or by the operating system (a "fatal exception"). In the former instance, the program contains code which catches the error and, as a result, returns to the operating system or calls an operating system service to terminate the program.
(1997-08-03)