Bible Dictionaries
Underclay

Webster's Dictionary

(n.) A stratum of clay lying beneath a coal bed, often containing the roots of coal plants, especially the Stigmaria.

Bibliography Information
Webster, Noah. Entry for 'Underclay'. Noah Webster's American Dictionary. https://www.studylight.org/​dictionaries/​eng/​web/​u/underclay.html. 1828.