Any substance or organism that cleans a setting by removing dirt, decaying matter, or some other unwanted material. Vultures are typical biological scavengers because they feed on the carcasses of dead animals. Certain chemicals can act as scavengers in chemical reactions. Lithium and magnesium are used in the metal industry as scavengers since these metals react with and remove small amounts of oxygen and nitrogen from molten metals. Even rain and snow can be regarded as scavengers because they wash pollutants out of the atmosphere.