资料来源 : pyDict

地面下的土壤;底土

资料来源 : Webster's Revised Unabridged Dictionary (1913)

Undersoil \Un"der*soil`\, n.
   The soil beneath the surface; understratum; subsoil.

资料来源 : WordNet®

undersoil
     n : the layer of soil between the topsoil and bedrock [syn: {subsoil}]