1. An inert powder added to a base material such as a paint, pigment, adhesive or concrete. Fillers may serve multiple purposes such as: extend a matrix, dilute a colour, decrease cost, provide bulk, increase strength, improve working properties or generally enhance performance. Examples of materials that are used as fillers are: acrylics, calcium carbonate, barium sulphate, clays, diatomaceous earth, glass fibres, glass spheres, gypsum, sand, silicates, starches, talc, titanium dioxide. Finely divided inert material, such as pulverized limestone, silica, or colloidal substances are sometimes added to Portland cement, paint or other materials to reduce shrinkage, improve workability, or act as an extender. 2. A preparation made for filling gaps, cracks, pores or holes. Examples are Dental plaster, Polyfilla, mastic, Plasticwood, Metalux, gesso, steel stick, brummer stopper, spackling and wax. Synonyms: fillers; diluent; extender; reinforcing agent; gap filling adhesive; cement; lute; filling compound; fill; mastic. Museum of Fine Arts, Boston (2000); RS Means Building Glossary (undated). [J. Cassar, R. de Angelis]