https://doi.org/10.1351/goldbook.P04723
A graphite material with coherent crystallographic domains of limited size regardless of the perfection and preferred orientation (texture) of their crystalline structure.
Note:
The common use of the term polycrystalline graphite for polygranular graphite is in line with this definition but may be inexact because usually all grains of polygranular graphite are polycrystalline themselves. Polycrystalline graphite can exhibit a random orientation, more or less preferred orientation, or a highly oriented texture as in some pyrolytic graphites There is no sharp transition, however, between the typical polycrystalline texture and the 'single crystal-like' texture of highly oriented pyrolytic graphite (HOPG).
The common use of the term polycrystalline graphite for polygranular graphite is in line with this definition but may be inexact because usually all grains of polygranular graphite are polycrystalline themselves. Polycrystalline graphite can exhibit a random orientation, more or less preferred orientation, or a highly oriented texture as in some pyrolytic graphites There is no sharp transition, however, between the typical polycrystalline texture and the 'single crystal-like' texture of highly oriented pyrolytic graphite (HOPG).