(1) an amorphous variety of kaolin of varying composition, containing an aluminum magnesium silicate. The name is derived from an ancient process of cleansing or "fulling" wool to remove the oil and dirt particles with a water slurry of earth or clay. (2) a refined clay sometimes used as a dusting powder or applied moistened with water as a form of poultice. Currently refers to any clay that can be used for the purpose of decolorizing in oil refining. Used as decolorizer for oils and other liquids, filtering medium, filler for rubber, and in agricultural formulations. [fr. fulling, an old process of cleaning wool, with earth or clay]