| Noun | 1. | fossil fuel - fuel consisting of the remains of organisms preserved in rocks in the earth's crust with high carbon and hydrogen contentcoal - fossil fuel consisting of carbonized vegetable matter deposited in the Carboniferous period fuel - a substance that can be consumed to produce energy; "more fuel is needed during the winter months"; "they developed alternative fuels for aircraft" natural gas, gas - a fossil fuel in the gaseous state; used for cooking and heating homes | |