What does "saturated" mean?

Saturated: (Chem.) Having its affinity satisfied; combined with all it can hold; - - said of certain atoms, radicals, or compounds; thus, methane is a saturated compound. Contrasted with unsaturated. Note: A saturated compound may exchange certain ingredients for others, but can not take on more without such exchange. Saturated color (Optics), a color not diluted with white; a pure unmixed color, like those of the spectrum.