Meaning

• A black rock formed from prehistoric plant remains, composed largely of carbon and burned as a fuel.

  "Put some coal on the fire."

• A piece of coal used for burning (this use is less common in American English)

  "Put some coals on the fire."

• A type of coal, such as bituminous, anthracite, or lignite, and grades and varieties thereof.

• A glowing or charred piece of coal, wood, or other solid fuel.

  "Just as the camp-fire died down to just coals, with no flames to burn the marshmallows, someone dumped a whole load of wood on, so I gave up and went to bed."

• Charcoal.

Meaning

• To take on a supply of coal (usually of steam ships).

• To supply with coal.

  "to coal a steamer"

• To be converted to charcoal.

• To burn to charcoal; to char.

• To mark or delineate with charcoal.