'Plumbago' definitions:

Definition of 'plumbago'

noun

Used as a lubricant and as a moderator in nuclear reactors [syn: graphite, black lead, plumbago]

noun

Any plumbaginaceous plant of the genus Plumbago

From: GCIDE

Plumbago \Plum*ba"go\, n. [L., from plumbum lead.]
1. (Min.) Same as Graphite. [1913 Webster]
2. (Bot.) A genus of herbaceous plants with pretty salver-shaped corollas, usually blue or violet; leadwort. [1913 Webster] Plumbean

From: GCIDE

Graphite \Graph"ite\, n. [Gr. gra`fein to write: cf. F. graphite. See Graphic.] (Min.) Native carbon in hexagonal crystals, also foliated or granular massive, of black color and metallic luster, and so soft as to leave a trace on paper. It is used for pencils (improperly called lead pencils), for crucibles, and as a lubricator, etc. Often called plumbago or black lead. [1913 Webster]
Graphite battery (Elec.), a voltaic battery consisting of zinc and carbon in sulphuric acid, or other exciting liquid. [1913 Webster]