Short for "Abnormal end." An abend is an unexpected or abnormal end to a process. In computer software, it typically refers to a software crash when a program unexpectedly quits. For example, an error in a program's code may cause it to freeze or crash while running a certain command. The result is an unexpected (and often inconvenient) end to the program.
The term "ABEND" was initially used by IBM OS/360 systems as an error message. It is now used by Novell Netware systems and also as a general programming term.