Definition of coal ball in English:

coal ball

noun

  • 1A ball made of coal dust, for use as fuel (now rare).

  • 2Geology a rounded mass of calcite or pyrite containing fossilized plant remains, typically found in or near coal seams.

Origin

Early 17th century; earliest use found in Hugh Platt (bap. 1552, d. 1608), writer on agriculture and inventor.