A bed of coal is a common phrase used to describe a layer of coal in the ground. However, there are several synonyms that can be used to describe the same thing. One of the most popular alternatives is the term 'coal seam'. A coal seam refers to a layer of coal that has been formed over time in the earth. Other synonyms for bed of coal can include 'coal deposit', 'coal vein' or 'coal layer'. These terms all refer to the same thing and can be used interchangeably. Whatever term you choose to use, it's important to remember that coal is a valuable resource that has helped power the world for centuries.