1. the lowest or most basic unit in the natural system of soil classification; a subdivision of a soil series and consisting of or describing soils that are alike in all characteristics including the texture of the A horizon or plow layer —note the term was used in the US soil classification systems prior to publication of USDA's Soil Taxonomy (1975) 2. in Europe, soil type is roughly equivalent to a great soil group This definition last updated 10/07/2008