This is a way of cheating at video games. Basically, the player backs up game files (usually savegame files) and then restores them after dying. The result is that the player never really dies and beats the game much more quickly, taking much of the fun out of the game. As far as I know, this originated in the rec.games.roguelike.nethack newsgroup.
From the rec.games.rougelike.nethack newsgroup: "You should be aware, however, that there is a general consensus that savescumming is actually detrimental to the development of proper playing skills"