To heat a mass of fine particles of ceramic, metal, polymer or other substance to a temperature just below its melting point to form a single solid or porous mass depending on the size of the particles, or a mass formed in this way. Sintered clay has been fired to a point at which it can no longer be dissolved by water, but it may be that it has yet to vitrify. Metal powders are sintered when they have been fused into a cosive mass by heating them to just short of melting. Sintering is a widely-used manufacturing process. "Sinter" came to us from sintar; the same German word meaning metal slag from which English obtained "cinder."Also see polymer clay, solve, travertine, and vitrify.