Cylinder may refer to: Moving cylinders: Cylinder (engine), the space within which a piston travels in an engine Cylinder (steam locomotive) Hydraulic cylinder, a cylinder barrel with piston rod for pushing and pulling using pressurized fluid Pneumatic cylinder, a cylinder barrel with piston rod for pushing and pulling using compressed gases Cylinder (firearms), the rotating device that contains the firing chambers of a revolver Cylinder lock, the part of a lock that's profiled to accept… (More on Cylinder)