1. secretions of certain trees, or of insects feeding on them, which are oxidation or polymerization products of terpenes, consisting of mixtures of aromatic acids and esters insoluble in water but soluble in ether, alcohol, or other organic solvents —note 1. natural resins often exude from wounds and are obtained commercially by tapping or by extraction with solvents —note 2. natural resins are sometimes designated hard (having little essential oil and high melting points, like copal) or soft (with considerable amounts of essential oil and lower melting points, like oleoresin and balsam) 2. the resin actually present in the living tree, in contrast to the exuded resin, which is subject to immediate chemical change —synonym pitch —see wound gumThis definition last updated 10/27/2008