Definitions

from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun A fossilized material in shale and other sedimentary rock that yields oil upon heating.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun any organic matter present in a sedimentary rock that is insoluble in organic solvents; the precursor of oil and natural gas

Etymologies

from The American Heritage® Dictionary of the English Language, 4th Edition

[Greek kēros, wax + –gen.]

Examples

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