A chassis is the frame of a car. If you warp the chassis of your mom’s car when you make a Dukes of Hazzard jump, she's going to be mad. Pronounce chassis CHASS-ee (singular) and CHASS-eez (plural).
Chassis comes from the Latin capsa, meaning box. In the 1600s, chassis referred to window frames, and starting with early automobile production, acquired its dominant meaning, i.e., the box that is the frame for the car. It also means other kinds of frame/boxes too — if you have a radio or a stereo, the outside box is called a chassis.