subsoil plough1
/ˈsʌbsɔɪl ˌplaʊ/(US subsoil plow)
noun
A kind of plough with no mouldboard, used to loosen the soil at some depth below the surface without turning it up.
Origin
Early 19th century; earliest use found in American Farmer. From subsoil + plough.
subsoil-plough2
/ˈsʌbsɔɪl ˌplaʊ/(US subsoil-plow)
verb
[with object] To plough (land) with a subsoil plough.
Origin
Mid 19th century; earliest use found in Henry Stephens (1795–1874), writer on agriculture. From subsoil plough. Compare earlier sub-plough, sub, and subsoil.