Chassis/ˈʃæsiz/ Definition 1 of 3Pro Tip 1/3Vehicle Foundation The chassis is a vehicle's foundational structure, like a skeleton. A sturdy chassis is important for the vehicle's durability. Pro Tip 2/3Beyond Cars While often associated with cars, the term also applies to other vehicles like trucks and buses. The bus chassis was designed for heavy loads. Pro Tip 3/3Metaphorical Use Chassis can metaphorically refer to a person's body structure. The athlete had a well-built chassis.