What is the meaning of Coal?

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

A type of coal, such as bituminous, anthracite, or lignite, and grades and varieties thereof, as a fuel commodity ready to buy and burn.

A piece of coal used for burning

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

Charcoal.

Content of low quality.

 Bombs emitting black smoke on impact.

Money.

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

To supply with coal.

To be converted to charcoal.

To burn to charcoal; to char.

To mark or delineate with charcoal.

Failing to be humorous or of extremely poor quality.

Black like coal; coal-black.

To post low-quality content online.

Source: wiktionary.org