Usually a coal tar pitch or petroleum pitch (but may include thermosetting resins or mesophase pitch powders) which, when mixed with a binder coke or a filler, constitutes a carbon mix. This is used in preparation of the formation of shaped green bodies and subsequently carbon artifacts.
Source:
PAC, 1995, 67, 473. 'Recommended terminology for the description of carbon as a solid (IUPAC Recommendations 1995)' on page 477 (https://doi.org/10.1351/pac199567030473)