from The American Heritage® Dictionary of the English Language, 4th Edition
- n. Sedimentary rock composed of fine fragments, as of clay or mud.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A sedimentary rock containing very fine particles
from The Century Dictionary and Cyclopedia
- n. In petrol., a rock made up of very fine argillaceous sediment. It would include fireclay, brick-clay, fullers' earth, and similar deposits.
Greek pēlos, clay + -ite1.(American Heritage® Dictionary of the English Language, Fourth Edition)