coal 
(kōl)
(kōl)n.
1.
a. A natural dark brown to black graphitelike material used as a fuel, formed from fossilized plants and consisting of amorphous carbon with various organic and some inorganic compounds.
b. A piece of this substance.
2. A glowing or charred piece of solid fuel.
3. Charcoal.
v. coaled, coal·ing, coals
v.tr.
1. To burn (a combustible solid) to a charcoal residue.
2. To provide with coal.
v.intr.
To take on coal.
[Middle English col, from Old English.]