IPA: /ˈsʌbbeɪs/
KK: /sʌbbeɪs/
A layer or material that is placed underneath another layer to provide support or stability, often used in construction or road building.
The workers laid down a subbase of crushed stone before pouring the concrete for the road.
Subbase → It is formed from "sub-" (meaning under) and "base" (from Latin "basis", meaning foundation or base). The word "subbase" refers to a layer that is situated under the main base or foundation.
Think of something that is 'under' ('sub-') the main 'foundation' ('base') — that's why subbase means a layer beneath the main base.