pencil lead

English Thesaurus

1. mixture of graphite with clay in different degrees of hardness; the marking substance in a pencil (noun.artifact)

hypernym	:	black lead, graphite, plumbago,
definition	:	used as a lubricant and as a moderator in nuclear reactors (noun.substance)

part meronym	:	lead pencil,
definition	:	pencil that has graphite as the marking substance (noun.artifact)