Entry 1 sense Webster, 1913 Leucoline /(lū"kō̇*lĭn [or] -lēn)/ · Leu·co·line · IPA 01 n. A nitrogenous organic base from coal tar, and identical with quinoline. Cf. Quinoline. 1. A nitrogenous organic base from coal tar, and identical with quinoline. Cf. Quinoline.(Chem.) See: Quinoline