The Collaborative International Dictionary of English v.0.48:

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]

The Collaborative International Dictionary of English v.0.48:

Lead \Lead\ (l[e^]d), n. [OE. led, leed, lead, AS. le['a]d; akin
   to D. lood, MHG. l[=o]t, G. loth plummet, sounding lead,
   small weight, Sw. & Dan. lod. [root]123.]
   1. (Chem.) One of the elements, a heavy, pliable, inelastic
      metal, having a bright, bluish color, but easily
      tarnished. It is both malleable and ductile, though with
      little tenacity, and is used for tubes, sheets, bullets,
      etc. Its specific gravity is 11.37. It is easily fusible
      (melting point 327.5[deg] C), forms alloys with other
      metals, and is an ingredient of solder and type metal.
      Atomic number 82. Atomic weight, 207.2. Symbol Pb (L.
      Plumbum). It is chiefly obtained from the mineral galena,
      lead sulphide.
      [1913 Webster]

   2. An article made of lead or an alloy of lead; as:
      (a) A plummet or mass of lead, used in sounding at sea.
      (b) (Print.) A thin strip of type metal, used to separate
          lines of type in printing.
      (c) Sheets or plates of lead used as a covering for roofs;
          hence, pl., a roof covered with lead sheets or terne
          plates.
          [1913 Webster]

                I would have the tower two stories, and goodly
                leads upon the top.               --Bacon
          [1913 Webster]

   3. A small cylinder of black lead or graphite, used in
      pencils.
      [1913 Webster]

   Black lead, graphite or plumbago; -- so called from its
      leadlike appearance and streak. [Colloq.]

   Coasting lead, a sounding lead intermediate in weight
      between a hand lead and deep-sea lead.

   Deep-sea lead, the heaviest of sounding leads, used in
      water exceeding a hundred fathoms in depth. --Ham. Nav.
      Encyc.

   Hand lead, a small lead use for sounding in shallow water.


   Krems lead, Kremnitz lead [so called from Krems or
      Kremnitz, in Austria], a pure variety of white lead,
      formed into tablets, and called also Krems white, or
      Kremnitz white, and Vienna white.

   Lead arming, tallow put in the hollow of a sounding lead.
      See To arm the lead (below).

   Lead colic. See under Colic.

   Lead color, a deep bluish gray color, like tarnished lead.


   Lead glance. (Min.) Same as Galena.

   Lead line
      (a) (Med.) A dark line along the gums produced by a
          deposit of metallic lead, due to lead poisoning.
      (b) (Naut.) A sounding line.

   Lead mill, a leaden polishing wheel, used by lapidaries.

   Lead ocher (Min.), a massive sulphur-yellow oxide of lead.
      Same as Massicot.

   Lead pencil, a pencil of which the marking material is
      graphite (black lead).

   Lead plant (Bot.), a low leguminous plant, genus Amorpha
      (Amorpha canescens), found in the Northwestern United
      States, where its presence is supposed to indicate lead
      ore. --Gray.

   Lead tree.
      (a) (Bot.) A West Indian name for the tropical, leguminous
          tree, Leuc[ae]na glauca; -- probably so called from
          the glaucous color of the foliage.
      (b) (Chem.) Lead crystallized in arborescent forms from a
          solution of some lead salt, as by suspending a strip
          of zinc in lead acetate.

   Mock lead, a miner's term for blende.

   Red lead, a scarlet, crystalline, granular powder,
      consisting of minium when pure, but commonly containing
      several of the oxides of lead. It is used as a paint or
      cement and also as an ingredient of flint glass.

   Red lead ore (Min.), crocoite.

   Sugar of lead, acetate of lead.

   To arm the lead, to fill the hollow in the bottom of a
      sounding lead with tallow in order to discover the nature
      of the bottom by the substances adhering. --Ham. Nav.
      Encyc.

   To cast the lead, or To heave the lead, to cast the
      sounding lead for ascertaining the depth of water.

   White lead, hydrated carbonate of lead, obtained as a
      white, amorphous powder, and much used as an ingredient of
      white paint.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Black lead \Black` lead"\
   Plumbago; graphite. It leaves a blackish mark somewhat like
   lead. See Graphite.
   [1913 Webster] Blacklead

WordNet (r) 3.0 (2006):

black lead
    n 1: used as a lubricant and as a moderator in nuclear reactors
         [syn: graphite, black lead, plumbago]