Short for "Abnormal End."
An abend (sometimes capitalized ABEND) is an error that causes an unexpected or abnormal end of a process. It is typically the result of a flaw in a programming instruction that the computer cannot understand. The effect of an abend can be the affected application unexpectedly quitting or becoming unresponsive, sometimes requiring a reboot to resolve.
The term "abend" comes from the IBM OS/360 database systems of the 1960s, where it was a common error code. Some causes of abend errors were dividing by zero, running out of storage space, or pointing to a memory address that the computer cannot access. The error code is also present in Novell Netware systems. Over time it has become a general programming term for a software-related crash.