sub·grade 
(sŭbgrād′)
(sŭbgrād′)n.
The level layer of rock or earth upon which the foundation of a road or railway is laid.
| 单词 | subgrade |
| 释义 | sub·grade (sŭbgrād′)n. The level layer of rock or earth upon which the foundation of a road or railway is laid. |
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