What is the meaning of Scumming?

The accumulation of sticky ink on a plate.

That which is scummed off; skimmings; scum.

The strategy of collecting easy rewards in unchallenging areas, e.g. when a high-level character visits levels suitable for low-level characters in roguelike games.

The act of restoring a game's save file, or restarting the game, for the purpose of continuing play with a better outcome than was obtained the first time.

Source: wiktionary.org