• (n.) A white crystalline substance which is obtained indirectly from the root of an umbelliferous plant (Imperatoria Oreoselinum), and yields resorcin on decomposition.
O`re·os'e·lin noun (Chemistry) A white crystalline substance which is obtained indirectly from the root of an umbelliferous plant ( Imperatoria Oreoselinum ), and yields resorcin on decomposition.