Harz hars kåda resin resina resina resina résine smola ρητίνη שרף harts תויה General term for solid or semisolid organic substance usually obtained from plant secretions, but sometimes obtained from insects or synthetically produced. It is soluble in organic solvent but not in water, and is commonly used in varnish, printing ink, and size. It is distinguished from gum by not being dissoluble in water. To distinguish between natural and synthetic resins, use the narrower terms natural resin or synthetic resin (AAT).