n. Black-lead; graphite. See graphite.n. [capitalized] [NL. (Tournefort, 1700).] A genus of plants, the leadworts, of the order Plumbagineæ and tribe Plumbageæ. characterized by a glandular calyx with five short erect teeth, a salver-shaped corolla with slender tube, free stamens, and five styles united into one nearly to the top.