basement
n. countable B2 Upper Intermediate Oxford US //ˈbeɪsmənt// UK //bˈeɪsmənt// base·ment
n. the floor of a building that is partly or completely below the ground. People often use it for storage, laundry, or as an extra living space.
n. the lowermost portion of a structure, located entirely or partially below ground level. Often serves as a foundation for the upper floors and provides space for utility systems or storage.
We keep our old boxes in the basement.
The family decided to renovate their damp basement into a bright home office and guest bedroom.
Engineers discovered that the building's basement had suffered significant water damage due to a crack in the foundation wall following the spring floods.
From base + -ment.
Usage
Commonly used with the preposition 'in' ('in the basement').