noun

1. a kind of dark brown to black, combustible, sedimentary rock resulting from the partial decomposition of vegetable matter away from air and under varying degrees of increased temperature and pressure over a period of millions of years: used as a fuel and in the production of coke, coal gas, water gas, and many coal-tar compounds
2. a piece (or collectively, pieces) of this rock
3. a piece of glowing or charred wood, coal, or similar substance; ember
4. charcoal

Etymology: ME & OE col, charcoal, live coal, akin to Ger kohle, ON kol < IE base *g(e)u-lo-, live coal > Ir gual

transitive verb

1. to reduce (a substance) to charcoal by burning
2. to provide with coal

intransitive verb