subbasement

[ suhb-beys-muh nt ]
/ ˈsʌbˌbeɪs mənt /

noun

a basement or one of a series of basements below the main basement of a building.

Origin of subbasement

First recorded in 1900–05; sub- + basement

British Dictionary definitions for subbasement

subbasement
/ (ˈsʌbˌbeɪsmənt) /

noun

an underground storey of a building beneath the main basement