Chassis

Chas"sis (?), n. The under part of an automobile, consisting of the frame (on which the body is mounted) with the wheels and machinery.

Chas"sis (?), n. [F. ch√Ęssis.] (Mil.) A traversing base frame, or movable railway, along which the carriage of a barbette or casemate gun moves backward and forward. [See Gun carriage.]