subsoil Syllabification: (sub·soil)Pronunciation: /ˈsəbˌsoil/Translate subsoil | into German Definition of subsoil noun the soil lying immediately under the surface soil. verb [with object] (usually as noun subsoiling) plow (land) so as to cut into the subsoil. subsoil in other Oxford dictionaries Definition of subsoil in the British & World English dictionary