ultisolEnglishOxford New American Dictionaryultisol /ˈəltəsäl, ˈəltəsɑl / ▸ noun Soil Science a highly weathered leached red or reddish-yellow acid soil with a clay-rich B horizon (subsoil), occurring in warm, humid climates. – ORIGIN 1960s : from ultimate + Latin solum ‘soil’.