A base frame, or movable railway, along which the carriage of a mounted gun moves backward and forward. / The base frame of a motor vehicle.

(electrical) A metal chassis, used as a base for electrical equipment, that is live because it lacks a transformer to isolate the equipment from the mains.

(computing) An electronics chassis, physically external to a host system, that provides a way to connect PCI Express cards to that host using the Thunderbolt interface.

(in combinations) having a particular type of chassis

Without a chassis.