black lead

English Thesaurus

1. used as a lubricant and as a moderator in nuclear reactors (noun.substance)

hypernym	:	atomic number 6, c, carbon,
definition	:	an abundant nonmetallic tetravalent element occurring in three allotropic forms: amorphous carbon and graphite and diamond; occurs in all organic compounds (noun.substance)

hyponym	:	lead, pencil lead,
definition	:	mixture of graphite with clay in different degrees of hardness; the marking substance in a pencil (noun.artifact)

hyponym	:	pencil,
definition	:	graphite (or a similar substance) used in such a way as to be a medium of communication (noun.substance)