underbody
/ˌʌndərbɒdi/Definitions
1. noun
The part of a vehicle, especially a car, that is underneath it, typically including the frame, engine, and suspension.
“The mechanic inspected the car’s underbody for any signs of damage.”
2. noun
In a building, the space underneath the main structure, such as a basement or cellar.
“The underbody of the building was used as a storage space.”