Understratum

[UNDER-¹ 5 c.] An underlying stratum or layer; a substratum.

1

1733. Tull, Horse-Hoeing Husb., xx. 290. These Drags draw them sometimes into larger Heaps, leaving the Under-Stratum bare betwixt them.

2

1783. Encycl. Brit. (ed. 2), X. 8307/1. However great differences there may be among the under strata.

3

1807. Vancouver, Agric. Devon (1813), 19. The soil and understrata of Little Torrington.

4

1886. 19th Cent., Sept., 421. There is a vast and virtuous understratum in society which really loves the right.

5