subsoil /ˈsʌbsɔɪl/noun 1verb 1forms 3 noun1 •The layer of earth that is below the topsoil.In the few areas underlain by horizontally bedded limestone, the surface soil is dark gray to black and peatlike, and the subsoil gray and marllike. — 1954 verb1 •To turn up the subsoil of. formssubsoiled · subsoiling · subsoils
