fossil fuel 
noun
A natural fuel such as coal or gas, formed in the geological past from the remains of living organisms.So burning coal or oil, which releases carbon from when the fossil fuel was formed, has a serious global warming effect....
- The second most prominent and naturally most abundant fossil fuel is coal.
- The surge in crude prices has prompted oil companies to boost exploration activities to discover more of the fossil fuel.
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- high-spiritedness
- high spirits
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- high-status
- high step
- high-stepper
- high-stepping
- high-stick
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- high stool
- high-strained
- high strained
- high street
- high-street bank
- high-street shop
- high strikes
- high-strung
- hight
- high table
- hightail
- high-tar
- high tea
- high-tech