The definition of a pollutant is waste or another contaminants that make something, such as the air or water, unclean.
Toxic waste is an example of a pollutant.
something that pollutes; esp., a harmful chemical or waste material discharged into the water or atmosphere
Origin of pollutant; from pollut(e) + -ant
Something that pollutes, especially a waste material that contaminates air, soil, or water.