subgrade

American  

[suhb-greyd] / ˈsʌbˌgreɪd /

noun

1. the prepared earth surface on which a pavement or the ballast of a railroad track is placed or upon which the foundation of a structure is built.

---

adjective

1. beneath the finished ground level of a project.

subgrade British  

/ ˈsʌbˌɡreɪd /

noun

1. the ground beneath a roadway or pavement

---

Etymology

Origin of subgrade

First recorded in 1895–1900; sub- + grade

Example Sentences

See Examples For:

subgrade

“We use top quality ingredients. No discounts or subgrade meats. Fresh veggies. All the side dishes are prepared by our staff,” she says.

From Los Angeles Times ● Jul. 20, 2026

“Reinforcing the ground below the tracks required removing any work already completed, excavating additional soil beneath 1400 feet of track, and installing new subgrade materials to provide the required stability,” according to WMATA.

From Washington Times ● Oct. 1, 2022

Section for Macadam Telford Foundation.—When the Telford type of foundation is employed, the earth subgrade is prepared and then the Telford stone placed carefully by hand.

From American Rural Highways by Agg, T. R. (Thomas Radford)

In level countries and with narrow roads, enough material may be excavated to raise the roadway above the subgrade in forming the side ditches by means of road machines.

From The Future of Road-making in America by Hulbert, Archer Bulter

Some engineers advocate that in preparing the subgrade, the earth be thoroughly rolled; others prefer not to roll the subgrade.

From American Rural Highways by Agg, T. R. (Thomas Radford)