Save scumming refers to the practice of copying your character's *.svg file to somewhere else on the hardware (usually a seperate backup folder), in order to reuse that file should the character in question die in game and have his save file deleted. Batch files may be written in order to automate the process.
Backing up your game to reload in case of a program crash is not considered save scumming. While technically it allows you to replay parts that you played before the crash, the crucial difference is that the character's death is (usually) your fault, while a program crash is not.
Characters that won through use of save scumming are generally not considered legitimate winners by the ADOM Community, nor are such characters accepted into the Hall of Fame; however, save scumming is useful for new players wishing to learn the basics of the game with minimal frustration, and for testing purposes.