Excretion is the physical process of eliminating waste, especially in a living organism. If you think about it, excretion keeps plumbers in business.
In a human, there are three organs that mostly take care of excretion, or ridding the body of substances it doesn't need: lungs, kidneys, and skin. All living things have some form of excretion — in people, some waste is excreted in the form of urine, while the excretion of plants results in carbon dioxide and water being released. Excretion comes from the French excrétion, with its Latin root excernere, "to discharge."