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Webster 1913 Edition

Underclay

Un′der-clayˊ

,

Noun.

(Geol.)

A stratum of clay lying beneath a coal bed, often containing the roots of coal plants, especially the

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Definition 2024

underclay

underclay

English

Noun

underclay ‎(plural underclays)

(geology) A stratum of clay lying beneath a coal bed.