any of various solid or semisolid, viscous, usually clear or translucent, yellowish or brownish, organic substances exuded from various plants and trees: natural resins are soluble in ether, alcohol, etc., and are used in varnishes and lacquers, as modifiers in synthetic plastics, etc.
Any of numerous clear to translucent yellow or brown, solid or semisolid, viscous substances of plant origin, such as copal, rosin, and amber, used principally in lacquers, varnishes, inks, adhesives, synthetic plastics, and pharmaceuticals.
Any of numerous physically similar polymerized synthetics or chemically modified natural resins including thermoplastic materials such as polyvinyl, polystyrene, and polyethylene and thermosetting materials such as polyesters, epoxies, and silicones that are used with fillers, stabilizers, pigments, and other components to form plastics.