subbasement.

A level below a building's main basement.

Use it for

Words that belong together

• subbasement storage
• descend to the subbasement

On the page

The records were stored in a subbasement below the boiler room.

Usage notes

Primary category: architecture / spatial description. Forms: Singular subbasement; plural subbasements. Legacy lexical fields mirror sense 1 only. Use numbered sense fields for all meanings. Established modern English lexical item. No separate regional spelling or grammatical inflection entry. Commonness: moderately common.